Chronic Kidney Disease: Why eGFR and Urine Albumin Must Be Read Together

Chronic kidney disease testing uses two complementary measurements: an eGFR test, usually calculated first from serum creatinine, and a urine albumin test, most often reported as the urine albumin-to-creatinine ratio (UACR). The eGFR test estimates how well the kidneys filter blood, while the urine albumin test helps identify kidney damage by detecting albumin leakage. Because either result can become abnormal before the other, both should be interpreted together, confirmed over time, and evaluated in the appropriate clinical context. For adults at risk for chronic kidney disease (CKD), KDIGO recommends estimating the GFR category with a combined creatinine–cystatin C equation when cystatin C is available. The Estimated Glomerular Filtration Rate (eGFR) with Creatinine and Cystatin C test may improve precision, but it does not replace UACR testing or diagnose CKD by itself.¹

This article is educational. Laboratory results do not replace a medical history, examination, imaging, medication review, or care from a qualified healthcare professional.

Key Takeaways

• eGFR estimates filtration; urine albumin helps identify kidney damage. Neither replaces the other.
• A person can have persistent albuminuria with an eGFR above 60, or a low eGFR with little albumin in the urine.
• CKD generally requires a kidney abnormality that persists for at least three months, unless other evidence already establishes chronicity.
• Kidney risk is classified by cause, GFR category, and albuminuria category, often abbreviated CGA.
• A first-morning urine sample is preferred for confirming an elevated random urine albumin result.
• Creatinine-based eGFR is the usual initial filtration estimate. In adults at risk for CKD, KDIGO recommends using the combined creatinine-cystatin C estimate to assign the GFR category when cystatin C is available; the combined estimate is especially useful when creatinine may be inaccurate or a clinical decision depends on GFR.¹
• Sudden kidney changes, very low urine output, severe swelling, breathing difficulty, confusion, or symptoms of a dangerous electrolyte imbalance require prompt medical evaluation.

This guide focuses on interpreting results. For causes, symptoms, and the diagnostic process, read CKD stages, causes, symptoms, and tests. For choosing among specimens and panels, see the kidney function testing overview.

What Is Chronic Kidney Disease?

Chronic kidney disease is an abnormality of kidney structure or function that has implications for health and persists for at least three months. The definition does not depend on one creatinine number or an eGFR label alone. A persistent eGFR below 60 mL/min/1.73 m², persistent albuminuria, blood or abnormal sediment in the urine, structural changes, or certain inherited kidney disorders can establish the pattern when evaluated in context.¹

The kidneys filter waste and extra water, regulate electrolytes and acid-base balance, help control blood pressure, support red-blood-cell production, and participate in mineral and bone metabolism. CKD can therefore affect cardiovascular health, fluid balance, blood counts, medication handling, and bone health long before a person associates symptoms with the kidneys.

Early CKD is often silent. Fatigue, swelling, foamy urine, changes in urination, nausea, itching, cramps, or reduced exercise tolerance may occur, but these symptoms are not specific. Objective blood and urine testing can identify patterns that symptoms alone cannot, while imaging, examination, and sometimes specialist evaluation are needed to determine cause and severity.

Why eGFR and Urine Albumin Must Be Read Together

KDIGO recommends testing people at risk for CKD with both urine albumin measurement and an assessment of GFR.¹ NIDDK likewise describes GFR and urine albumin as the two principal tests used to detect and monitor kidney disease.² Their roles are different:

Question	eGFR	Urine albumin-to-creatinine ratio	Why both matter
What does it reflect?	Estimated filtration of blood	Albumin leakage through the kidney filters	Function and damage are related but not identical
Can it be abnormal first?	Yes; filtration can fall with little albuminuria	Yes; albumin can rise while eGFR remains above 60	Testing only one can miss an important pattern
How is it commonly obtained?	Calculated from a serum creatinine test; cystatin C may be added	Measured with an UACR test on a spot urine sample	The blood and urine samples answer separate questions
What can distort it?	Muscle mass, recent meat intake, creatine use, illness, medication effects, and assay variation	Exercise, urinary infection, fever, bleeding, hydration, and collection conditions	Unexpected results often require repeat testing under comparable conditions
What does it not establish alone?	Cause, chronicity, structural disease, or kidney damage with preserved filtration	Filtration level, cause, or whether one elevated result is persistent	Clinical history, trends, urinalysis, and sometimes imaging are still necessary

Four Patterns That Explain the Difference

1. eGFR above 60 with UACR below 30: CKD is not established by these two measurements alone. Other persistent markers of kidney damage could still matter.
2. eGFR above 60 with UACR at or above 30: Persistent albuminuria can indicate kidney damage even when filtration appears preserved.
3. eGFR below 60 with UACR below 30: Persistent reduced filtration can meet the CKD criterion even with little albuminuria. Age, vascular disease, prior injury, and medications may affect the cause and interpretation; they do not automatically negate a persistent CKD-range result.
4. eGFR below 60 with elevated UACR: Both filtration loss and albumin leakage are present; higher albuminuria generally indicates greater kidney and cardiovascular risk within the same GFR category.

Examples: What Different Paired Results Can Mean

The following are fictional educational examples, not patient records or instructions to diagnose yourself. eGFR values use mL/min/1.73 m²; UACR values use mg/g. Persistent means that chronicity has been established, usually over at least three months.

Illustrative pattern	What it may mean	Question for the clinician
eGFR 96; UACR 8	These two results do not establish CKD. Structural disease or other persistent kidney findings could still matter.	Is there another reason to investigate kidney health?
eGFR 96; UACR 180 persistently	Filtration appears preserved, but persistent albuminuria can establish kidney damage.	What explains the albuminuria, and what follow-up is needed?
eGFR 42 persistently; UACR 12	Reduced filtration can meet the CKD criterion despite little urine albumin.	What is the likely cause of the reduced filtration?
eGFR 42; UACR 850 persistently	Both filtration loss and marked albuminuria are present. The combined pattern carries more risk than the same eGFR with little albuminuria.	How should cause, progression risk, and specialist care be assessed?
UACR 90 after strenuous exercise; 8 on a later first-morning sample	A temporary increase is possible; this sequence alone does not establish persistent albuminuria.	Are further samples needed under comparable conditions?
eGFR 54 once during illness; UACR below 30	Acute illness, volume changes, and medication effects may contribute. CKD is not established by one result.	How soon should this be reassessed, and is acute kidney injury a concern?

Interpret these patterns with the clinical history, urine findings, and evidence of persistence. KDIGO CKD evaluation guidance.

How GFR and Albuminuria Categories Work

KDIGO classifies CKD by cause, GFR category, and albuminuria category, abbreviated CGA. The two laboratory axes are shown below. They are classification categories, not standalone diagnoses or individualized treatment targets.¹

GFR Categories

Category	eGFR (mL/min/1.73 m2)	Description
G1	90 or higher	Normal or high
G2	60-89	Mildly decreased
G3a	45-59	Mildly to moderately decreased
G3b	30-44	Moderately to severely decreased
G4	15-29	Severely decreased
G5	Below 15	Kidney failure category

G1 or G2 does not establish CKD without another persistent marker of kidney damage. An eGFR below 60 can support CKD when it persists for at least three months or when other evidence establishes chronicity.

Albuminuria Categories

Category	UACR (mg/g)	Description
A1	Below 30	Normal to mildly increased
A2	30-300	Moderately increased
A3	Above 300	Severely increased

A result at or above 30 mg/g on a random sample should generally be confirmed with a subsequent first-morning midstream sample. A single elevated result can be temporary; a persistent result carries different meaning.¹

Why the Combination Changes Risk

Two people with the same eGFR may have different risks if their urine albumin results differ. A G3a-A1 pattern generally carries less kidney-progression risk than G3a-A3. Conversely, G2-A3 can reflect meaningful kidney damage despite an eGFR above 60. The cause of the kidney pattern further changes risk and management, which is why CKD should not be reduced to a single stage number.

When Can Cystatin C Clarify an Unexpected Result?

Creatinine-based eGFR is the usual starting estimate. KDIGO recommends using the combined creatinine–cystatin C estimate for GFR categorization in adults at risk for CKD when cystatin C is available, particularly when creatinine may be inaccurate and a clinical decision depends on filtration. Neither marker measures urine albumin leakage. KDIGO, sections 1.1–1.2.

For example, a creatinine-based eGFR of 52 and combined estimate of 71 may prompt reconsideration of filtration classification; a combined estimate of 43 may reinforce concern about reduced filtration. These illustrative differences do not prove which result is correct or establish CKD without the rest of the evaluation. Do not manually average two reported estimates.

For non-kidney influences, discordant results, and medication-related considerations, read Cystatin C Test: When It Can Improve eGFR Accuracy.

A Focused Approach to Confirmation and Cause

Start with a defined question: screening because of risk, explaining an unexpected finding, or monitoring known disease. Creatinine with eGFR and UACR provide the two core measurements. Urinalysis can add information about blood, cells, casts, and other urinary abnormalities when evaluating the cause.

Confirm unexpected findings, assess urgency, and review earlier reports before applying a chronic diagnosis. Blood in urine with substantial protein loss or a rapid fall in filtration needs a different investigation from a stable pattern in longstanding diabetes. Imaging, specialist-selected testing, or biopsy may be needed; a large blood panel cannot substitute for that evaluation.

Which Additional Tests Address a Specific Question?

Choose additional tests according to symptoms, prior abnormalities, and the care plan. A larger order is not automatically more useful.

Question	Relevant test or panel	Limitation
Filtration accuracy	Creatinine Test; Cystatin C with eGFR; Estimated Glomerular Filtration Rate with Creatinine and Cystatin C	An estimate does not establish cause, chronicity, or urine albumin loss.
Albumin or other urinary abnormalities	Albumin Random Urine Test with Creatinine; Urinalysis Complete Test	A positive urine dipstick does not replace quantitative UACR.
General chemistry context	Basic Metabolic Panel or Comprehensive Metabolic Panel	Neither replaces urine albumin measurement; confirm panel components before ordering overlapping tests.
Falling hemoglobin or possible anemia	Complete Blood Count with Differential and Platelets; Reticulocyte Count; Ferritin, Iron and Total Iron Binding Capacity Panel	CKD is only one possible contributor; ferritin and TSAT need interpretation together.
Electrolyte and acid-base monitoring	Potassium Test; Carbon Dioxide Test	Total CO2 largely reflects bicarbonate; an abnormal value does not establish its cause.
Mineral and bone complications	Calcium Test; Phosphate (as Phosphorus) Test; PTH Intact Test; Vitamin D 25-Hydroxy Total Immunoassay Test	Use stage, trends, and clinician guidance; not a universal screening bundle.
Related diabetes or cardiovascular risk	Hemoglobin A1c Test; Lipid Panel Test	These inform related risks rather than diagnose CKD.
Low blood albumin	Albumin Test	Urinary loss, inflammation, liver disease, and nutrition can contribute; this is different from UACR.

The 2026 KDIGO anemia guidance includes CBC, reticulocytes, ferritin, and TSAT in the initial anemia evaluation. Low hemoglobin should not automatically be attributed to reduced kidney hormone production. KDIGO 2026 anemia guidance.

How to Prepare for Kidney Testing and When to Repeat It

Preparation depends on the specific tests ordered. Review the current instructions for each product and tell the healthcare professional interpreting the results about medications, supplements, recent illness, and unusual exercise. Do not stop a prescribed medicine or supplement solely to prepare for testing unless the prescribing professional directs you to do so.

Preparing for the Blood Sample

• Ask whether fasting is required for the complete order. The kidney tests alone may not require fasting, but glucose or lipid testing may change the instructions.
• Avoid intentionally dehydrating or overhydrating before collection. Aim for usual fluid intake unless a clinician has given different instructions.
• Report recent vomiting, diarrhea, fever, infection, heavy exercise, or major dietary changes.
• Report creatine supplements, high-dose supplements, and medications that may change creatinine, potassium, or kidney blood flow.
• For the most comparable trends, use similar collection conditions and, when practical, the same laboratory method.

Preparing for the Urine Sample

For a spot urine albumin-to-creatinine ratio test, a first-morning midstream sample is preferred for confirmation because it generally has less within-person variability. A random sample is acceptable for initial testing when a first-morning sample is not available.¹

Factor	Possible effect	Practical guidance	Important caution
Strenuous exercise	Can temporarily increase urine albumin	Avoid intense exercise for about 24 hours when feasible and appropriate	Do not delay evaluation of concerning symptoms
Urinary infection or fever	Can raise albumin or produce other abnormal urine findings	Document symptoms and obtain clinical guidance about timing	Infection symptoms may require prompt assessment rather than routine retesting
Menstrual or urinary bleeding	Can affect albumin, protein, and blood measurements	Document the circumstance and follow collection guidance	Visible blood in urine outside menstruation requires medical evaluation
Dehydration or very dilute urine	Changes concentration; the ratio corrects for some, but not all, variation	Use usual hydration and note unusual fluid loss or intake	Severe dehydration can cause acute kidney injury
Acute illness or unstable blood pressure or glucose	Can cause a temporary change in albumin excretion	Interpret with the clinical timeline and consider confirmation after stabilization	Urgent abnormalities should not wait three months for follow-up

Why One Abnormal Result Is Usually Not Enough

KDIGO advises repeating an incidentally elevated ACR, hematuria, or low eGFR to confirm CKD. The usual three-month definition is about chronicity, not a rule to ignore urgent findings. A rapidly rising creatinine, a marked fall in eGFR, severe electrolyte disturbance, or concerning urine sediment needs timely medical assessment.¹

Does “Microalbumin” Mean a Different Protein?

No. Microalbumin is older terminology for measuring small amounts of the same albumin protein. A spot UACR compares urine albumin with urine creatinine, helping account for urine concentration. A Microalbumin, 24-Hour Urine with Creatinine collection answers a related question over a full day, but incomplete collection can distort the result. It is not automatically better than a spot UACR or required for routine CKD assessment. Follow the specific order and collection instructions. KDIGO urine albumin assessment.

How to Understand eGFR, UACR, and Kidney Trends

Interpretation should separate four ideas. The broader guide to reading and understanding lab results explains reference intervals, thresholds, flags, units, and trends in more detail.

Term	What it means	Why it may differ	Patient caution
Laboratory reference interval	The range used by a laboratory to flag results	Method, population, specimen, and laboratory practices	A result inside the interval does not rule out CKD
CKD decision threshold	A guideline value used with persistence and context, such as eGFR below 60 or UACR at or above 30 mg/g	Clinical purpose, chronicity, age, and other kidney markers	A threshold is not an automatic diagnosis from one sample
Monitoring target	An individualized goal used during care	Cause, risk, medications, comorbidities, and tolerance	Do not substitute a generic online target for a personal care plan
Trend	Change across comparable measurements over time	Biological, analytical, and preanalytical variation	Small fluctuations may not mean disease progression

Meaningful Changes Require Context

For people with CKD, KDIGO states that an eGFR change greater than 20% on a subsequent test exceeds expected variability and warrants evaluation. After starting a treatment that changes kidney hemodynamics, a fall greater than 30% also warrants evaluation. For albuminuria monitoring, a doubling of UACR exceeds expected laboratory variability. These are signals for assessment, not instructions to change medication without professional guidance.¹

How Often Should eGFR and Urine Albumin Be Monitored?

There is no single schedule for everyone. KDIGO recommends assessing GFR and albuminuria at least annually in people with CKD and more often when progression risk is higher or the result will affect a clinical decision.¹ Diabetes guidance recommends annual eGFR and spot UACR screening for everyone with type 2 diabetes and for people with type 1 diabetes of at least five years' duration.⁴

Monitoring frequency may increase after a meaningful change in kidney results, a relevant medication change, an acute illness, or development of a complication. It may decrease when risk is low and results are stable. A clinician should determine the schedule based on the CGA pattern, cause, comorbidities, and treatment plan.

Risk-Based Referral Is More Informative Than eGFR Alone

For people with CKD G3-G5, KDIGO recommends using an externally validated kidney-failure risk equation. A five-year kidney-failure risk around 3%-5% may support nephrology referral alongside eGFR, UACR, urine findings, and other clinical considerations. Referral may also be appropriate for uncertain cause, rapid progression, persistent hematuria, very high albuminuria, resistant hypertension, persistent electrolyte or acid-base abnormalities, or CKD-related anemia or bone disease.¹

A risk equation estimates the chance of a future outcome; it does not diagnose kidney failure or predict exactly when it will occur. The commonly used four-variable Kidney Failure Risk Equation uses age, sex, eGFR, and UACR in appropriate CKD G3–G5 populations. It should be applied with a validated equation and clinical review, not extrapolated automatically to G1–G2 or an acute kidney injury. KDIGO risk assessment, chapter 2.

When Prompt or Emergency Evaluation Is Needed

Routine direct-access testing is not a substitute for urgent care. Seek prompt medical assessment for:

• A sudden substantial rise in creatinine or fall in eGFR
• Markedly reduced urine output or inability to urinate
• New visible blood or dark urine
• Rapidly increasing swelling
• Severe vomiting or diarrhea with dehydration
• Shortness of breath, chest symptoms, or inability to lie flat
• Confusion, fainting, severe weakness, or a seizure
• Severe flank pain with fever
• A critically abnormal Potassium Test result or marked weakness, palpitations, or an abnormal heartbeat
• A new kidney abnormality, hypertension, or proteinuria during pregnancy

These findings may reflect acute kidney injury, obstruction, infection, glomerular disease, dangerous electrolyte imbalance, or severe fluid retention.

How Ulta Lab Tests May Help

Eligible customers can review available kidney-related tests online, see current pricing before ordering, complete the required ordering process, visit an available collection location, and access results through an online account. The results can support a more informed conversation with a qualified healthcare professional. Review how direct-access laboratory testing works and what to expect, including ordering, preparation, collection, results, and responsible follow-up.

Direct-access testing is most useful when the test matches a clear question, preparation instructions are followed, and abnormal or changing results receive appropriate follow-up. It does not replace professional assessment of acute symptoms, medication safety, imaging, or a suspected complex kidney disorder.

Questions to Ask a Healthcare Professional

1. Do my eGFR and UACR results tell the same story or different stories?
2. Is this result likely to be acute, temporary, or chronic?
3. What previous results can establish a trend or chronicity?
4. Should an elevated random UACR be repeated with a first-morning sample?
5. Could muscle mass, exercise, diet, supplements, illness, or medication affect my creatinine-derived eGFR?
6. Would cystatin C or a combined creatinine-cystatin C estimate change a clinical decision?
7. Does my urinalysis suggest blood, infection, or an active urine-sediment pattern?
8. What is my complete cause-GFR-albuminuria classification?
9. Do I need testing for anemia, potassium, acid-base, or mineral and bone complications?
10. How often should eGFR and UACR be repeated for my risk level?
11. Would a kidney-failure risk equation or nephrology referral add useful information?
12. Do any symptoms or results require urgent evaluation rather than routine follow-up?

Frequently Asked Questions

Can you have chronic kidney disease with a normal eGFR?

Yes. Persistent albuminuria, blood or abnormal sediment in the urine, structural kidney abnormalities, or certain inherited disorders can establish CKD even when eGFR is 60 or higher. That is why a urine albumin-to-creatinine ratio test and other kidney-damage markers should be considered alongside eGFR.

Can urine albumin be normal when eGFR is low?

Yes. A reduced eGFR may occur with little albuminuria. Possible explanations include vascular disease, prior kidney injury, medication effects, age-related change, or a kidney disorder that does not produce substantial albumin leakage. Persistent results, the urinalysis, medical history, and sometimes imaging help clarify the pattern.

Does one low eGFR or high UACR result mean I have CKD?

Not automatically. CKD generally requires an abnormality that persists for at least three months or other evidence of chronic kidney damage. Dehydration, illness, infection, exercise, bleeding, medication effects, and acute kidney injury can alter results. Unexpected abnormalities should be repeated or evaluated on a timetable appropriate to their severity.

What is the difference between creatinine and eGFR?

Creatinine is a measured waste product in blood. eGFR is a calculated estimate of kidney filtration that uses the creatinine result and personal variables in a validated equation. A Creatinine Test may therefore report both the measured creatinine and an estimated GFR. Muscle mass and other non-kidney factors can influence the estimate.

Is microalbumin the same as UACR?

The older term microalbumin commonly refers to detecting moderately increased urine albumin, not a smaller type of albumin. UACR is the preferred quantitative ratio: it compares urine albumin with urine creatinine to reduce the effect of urine concentration. The Albumin Random Urine Test with Creatinine provides this relationship.

When can cystatin C add useful information?

A Cystatin C Test with eGFR may help when creatinine is likely to be less accurate because of unusual muscle mass, amputation, frailty, extreme exercise, diet, supplements, or illness. When greater accuracy is needed, the Estimated Glomerular Filtration Rate (eGFR) with Creatinine and Cystatin C generally provides a more accurate combined estimate than either marker alone, especially when staging, medication dosing, or another decision could change.

What if my creatinine-based and cystatin C-based eGFR results are different?

The estimates can differ because creatinine and cystatin C are affected by different non-kidney factors. Muscle mass, diet, supplements, medications, corticosteroid use, thyroid dysfunction, inflammation, smoking, adiposity, and acute illness may influence one marker more than the other. Do not manually average the two results. The laboratory-calculated Estimated Glomerular Filtration Rate (eGFR) with Creatinine and Cystatin C is generally more accurate when the two estimates disagree, although a healthcare professional may favor the less-affected marker or measured GFR when one marker has a strong known distortion.¹⁸

Do I need to fast for eGFR and urine albumin testing?

Fasting is not always required for the kidney measurements alone. It may be required when the order includes glucose, lipids, or another test with fasting instructions. Follow the current instructions for the complete order. Use usual hydration, disclose recent illness and supplements, and avoid intense exercise before urine albumin testing when feasible.

Why is a first-morning urine sample preferred?

A first-morning midstream sample generally has less within-person variability and correlates well with daily albumin excretion. KDIGO recommends confirming a random UACR at or above 30 mg/g with a subsequent first-morning sample. A random sample can still be used for initial testing when a first-morning sample is unavailable.

How often should eGFR and UACR be checked?

People with CKD generally need both assessed at least annually, with more frequent monitoring when progression risk is higher or results affect treatment decisions. Diabetes guidance recommends annual screening for everyone with type 2 diabetes and for people with type 1 diabetes of at least five years' duration. Individual schedules depend on risk and treatment.

When should a nephrologist be involved?

Referral may be appropriate for uncertain cause, rapid progression, very high albuminuria, persistent blood or casts in urine, resistant hypertension, persistent electrolyte or acid-base problems, CKD-related anemia or bone disease, or elevated predicted kidney-failure risk. The decision should combine eGFR, UACR, urine findings, symptoms, cause, and local referral practices.

Conclusion: Read Filtration, Damage, and Time Together

Chronic kidney disease testing is strongest when eGFR and urine albumin are interpreted as complementary measurements. A creatinine-derived eGFR offers a practical first estimate of filtration; a combined creatinine-cystatin C eGFR may improve accuracy when the decision requires it. UACR helps reveal albumin leakage and kidney damage. Urinalysis, complication testing, clinical history, and trends add context when the pattern requires it.

The central principle is simple: do not judge kidney health from creatinine alone, and do not interpret one elevated urine albumin result without confirmation and context. Use both kidney axes, determine whether abnormalities persist, classify cause-GFR-albuminuria risk, and review significant findings with a qualified healthcare professional. Explore kidney disease testing options and choose only the tests that answer a defined question.

Primary References

1. KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Disease: Improving Global Outcomes; published March 2024. Supports CKD definition and CGA classification; paired GFR and albumin testing; confirmation; cystatin C use; monitoring changes; and risk-based referral.
2. Chronic Kidney Disease Tests and Diagnosis. National Institute of Diabetes and Digestive and Kidney Diseases. Supports the complementary roles of GFR and urine albumin and the value of trends.
3. Identify and Evaluate Patients with Chronic Kidney Disease. National Institute of Diabetes and Digestive and Kidney Diseases. Supports risk-based testing and paired eGFR and spot UACR assessment.
4. Chronic Kidney Disease and Risk Management: Standards of Care in Diabetes - 2026. American Diabetes Association Professional Practice Committee; 2026. See also the ADA's 2026 CKD screening infographic. Supports annual spot UACR and eGFR screening in diabetes.
5. Estimated Glomerular Filtration Rate (eGFR). National Kidney Foundation; updated February 5, 2026. Supports patient-facing explanations of eGFR, creatinine limitations, and GFR estimation.
6. Urine Albumin-Creatinine Ratio (uACR). National Kidney Foundation; reviewed May 1, 2023. Supports quantitative UACR use, collection considerations, and interpretation of albuminuria.
7. eGFR Equations for Adults. National Institute of Diabetes and Digestive and Kidney Diseases; last reviewed May 2025. Supports the race-free 2021 CKD-EPI equations, the greater average accuracy of combined creatinine-cystatin C eGFR, and its use near critical decision values.
8. Clinical Measurements and eGFR Accuracy. National Institute of Diabetes and Digestive and Kidney Diseases; last reviewed May 2025. Supports non-GFR influences on creatinine and cystatin C and the rationale for combining the two markers.
9. Determining Drug Dosing in Adults with Chronic Kidney Disease. National Institute of Diabetes and Digestive and Kidney Diseases. Supports use of combined creatinine-cystatin C eGFR near drug-dosing cutoffs, body-surface-area considerations, and measured GFR when unusually high dosing accuracy is needed.

Disclosure: Ulta Lab Tests offers laboratory-testing services and may link to tests or panels discussed on this page. This content is educational and does not provide individual diagnosis or treatment

Originally published: August 7, 2026 | Updated: September 20 2026