Your estimated glomerular filtration rate, or eGFR, may look similar to your last result, yet your clinician may still want to check potassium, bicarbonate, and blood counts. These tests answer questions about kidney disease that a filtration estimate cannot answer by itself.
CKD monitoring looks at both kidney function and its effects on the body. Potassium testing helps assess electrolyte safety, bicarbonate-related testing helps evaluate acid-base balance, and anemia testing examines oxygen-carrying capacity and red blood cell production. The useful combination depends on your previous results, symptoms, medications, and treatment plan.
This guide focuses on adults with established chronic kidney disease, especially those who are not receiving dialysis. Dialysis and kidney-transplant teams use additional, individualized monitoring protocols. For an introduction to the full range of kidney tests, see Kidney Function Tests: eGFR, Creatinine, Cystatin C, uACR, and Urinalysis.
Think of your follow-up appointment as a review of several related questions. Is kidney filtration changing? Are medications being tolerated? Is there a new problem that needs attention even if filtration appears stable?
| Monitoring test | Main question | Important limitation |
|---|---|---|
| Potassium | Is the blood potassium level appropriate for normal nerve, muscle, and heart function? | Medications, acute illness, and specimen problems can affect the result. |
| Total carbon dioxide, commonly reported as CO2 | Is there a possible bicarbonate-related acid-base disturbance? | A low result does not establish its cause or measure blood pH directly. |
| Complete blood count, or CBC | Is hemoglobin falling, and what other blood-cell changes are present? | A CBC identifies an anemia pattern but does not prove that CKD caused it. |
| Ferritin and transferrin saturation, or TSAT | Are iron stores and available circulating iron adequate for blood-cell production? | Inflammation and recent treatment can complicate interpretation. |
| Reticulocyte count | Is the bone marrow producing an appropriate number of new red blood cells? | It must be interpreted with the degree of anemia and the other results. |
These tests supplement ongoing creatinine/eGFR and urine albumin-to-creatinine ratio, or uACR, monitoring. For help understanding those two measurements together, read Chronic Kidney Disease: Why eGFR and Urine Albumin Must Be Read Together.
Potassium helps nerves, muscles, and the heart work properly. The kidneys help keep its blood concentration within a suitable range by adjusting how much leaves the body in urine. CKD can reduce the ability to remove excess potassium. A high blood potassium level is called hyperkalemia. MedlinePlus: potassium and kidney function
Potassium is also a medication-safety measurement. A clinician may request it after a prescription change, during an illness, or after a previous abnormal result. Some diuretics and gastrointestinal losses can lower potassium, so CKD does not mean the level will always be high. MedlinePlus: potassium blood test
The question is more specific than “Is my potassium flagged?” It is: “How different is this from my usual level, what changed recently, and how quickly does it need to be assessed?” Use the reference interval and units on your own laboratory report.
A review may include prescribed medications, over-the-counter products, potassium supplements, salt substitutes containing potassium chloride, recent illness, and changes in food or drink intake. Several contributors can occur together. Having a high result does not automatically mean that ordinary fruits and vegetables are the sole cause. Dietary changes should be individualized with the healthcare team or a kidney dietitian. National Kidney Foundation: causes and nutrition considerations
Yes. Hemolysis—damage to blood cells during collection or handling—can release potassium into the sample. A clinician may request a prompt repeat sample when collection details suggest an error. MedlinePlus: falsely elevated potassium
Repeated fist pumping during collection can also affect the result. MedlinePlus: collection effects
Never assume that a high result is a collection error because you feel well. Dangerous hyperkalemia may have few symptoms. Follow urgent instructions from the laboratory or healthcare team immediately. National Kidney Foundation: hyperkalemia symptoms
That decision belongs to the prescribing clinician. KDIGO notes that potassium elevations associated with ACE inhibitors or ARBs can often be managed while preserving treatment. The response depends on severity, kidney function, blood pressure, and whether the abnormality can be controlled. Do not independently stop or adjust a prescription. KDIGO 2024 CKD guideline executive summary, section 3.6
Bicarbonate helps buffer acids. On a routine chemistry panel, the result labeled carbon dioxide or CO2 largely reflects bicarbonate. It provides acid-base information; it is not an oxygen-saturation measurement or a direct blood-pH measurement. MedlinePlus: carbon dioxide in blood
When kidneys have difficulty maintaining acid-base balance, bicarbonate can fall. This may be part of metabolic acidosis. However, a low total CO2 result can also occur with prolonged diarrhea, certain breathing-related disturbances, or other illnesses. The clinical context determines the next step. MedlinePlus: interpreting CO2 results
Ask your clinician to interpret a low result alongside the other chemistry measurements, recent symptoms, medications, and prior values. An unexpected result may need confirmation or additional clinical testing. A person with acute illness needs a different response from someone with a stable, mildly low value under an established monitoring plan.
No. KDIGO 2024 gives bicarbonate below 18 mmol/L in adults as an example of acidosis with potential clinical implications for which treatment should be considered. This is not a universal instruction to start treatment, and values above that level may still warrant evaluation. When treatment is used, monitoring includes bicarbonate, blood pressure, potassium, and fluid status. KDIGO 2024 CKD guideline executive summary, section 3.10
Do not use baking soda or an over-the-counter alkalinizing product to correct a laboratory flag on your own. Discuss what the result means and whether a specific intervention is appropriate.
Healthy kidneys make erythropoietin, a hormone that signals the bone marrow to produce red blood cells. CKD may reduce that signal. Anemia can contribute to fatigue, reduced exercise tolerance, dizziness, and breathlessness, although those symptoms have many possible causes. NIDDK: anemia in chronic kidney disease
A falling hemoglobin level should not automatically be labeled “kidney anemia.” Iron deficiency, blood loss, inflammation, vitamin deficiencies, and other conditions may contribute. More than one cause can be present. NIDDK: causes and evaluation of CKD anemia
The updated KDIGO 2026 anemia guideline includes CBC, reticulocytes, ferritin, and TSAT in the initial laboratory evaluation. This combination assesses the anemia, the marrow response, and iron status. KDIGO 2026 anemia guideline: key takeaways
The CBC measures hemoglobin and provides red-cell information such as mean corpuscular volume, or MCV. It also examines white blood cells and platelets. These accompanying findings help determine whether the pattern calls for a broader evaluation. A hemoglobin value should be compared with the appropriate laboratory range, previous values, symptoms, and treatment history.
For a fuller explanation of blood-count patterns, see CBC and Anemia Blood Tests: Hemoglobin, MCV, Iron, Ferritin, Vitamin B12, and Folate.
Ferritin provides information about stored iron. TSAT describes the percentage of iron-binding capacity occupied by iron and helps assess iron availability. Iron studies may report TSAT as “percent saturation.” Looking at the combination is more useful than treating one serum iron result as the whole answer. MedlinePlus: iron tests
Two patterns matter in CKD:
KDIGO 2026 uses these terms to distinguish different mechanisms. A normal or elevated ferritin therefore does not, by itself, establish that enough iron is available for red-cell production. KDIGO 2026 anemia guideline executive summary
Treatment decisions also depend on dialysis status, recent iron therapy, symptoms, and other findings. Do not use a general laboratory reference range as a self-treatment threshold.
Reticulocytes are newly produced red blood cells. Their number helps show how the bone marrow is responding to anemia or treatment. An inadequate response can occur with reduced production; an increased response can occur after blood loss, red-cell destruction, or recovery. The clinician interprets the count in relation to the hemoglobin level rather than judging the percentage in isolation. MedlinePlus: reticulocyte count
A routine CBC does not necessarily include a reticulocyte count. Check the actual order rather than assuming all blood-cell measurements are bundled together.
Vitamin B12 and folate testing may be appropriate when the history or initial blood results suggest a deficiency. Other investigations depend on the suspected cause. Unexplained or disproportionate anemia may require specialist assessment. NIDDK: diagnosing anemia in CKD
If iron deficiency is found, the evaluation may need to look for blood loss from the gastrointestinal tract, urinary tract, or menstrual bleeding. Identifying CKD does not remove the need to investigate another source of iron loss. KDIGO 2026 anemia guideline: evaluation pathways
There is no single schedule for every person or every test. Your plan should specify which measurements are due, when to collect them, who will review the results, and what should trigger an earlier call.
For anemia and iron-deficiency screening during CKD follow-up, KDIGO 2026 describes these reasonable intervals:
| CKD category | Guideline screening interval |
|---|---|
| G3 | At least annually |
| G4 | At least twice yearly |
| G5, including dialysis | At least every three months |
These are screening intervals, not instructions to wait when hemoglobin falls, symptoms develop, bleeding is suspected, or treatment changes. Active anemia treatment may require considerably closer monitoring. KDIGO 2026 anemia guideline executive summary
Potassium and chemistry testing often follow medication-specific plans. For example, KDIGO advises checking blood pressure, serum creatinine, and potassium within 2–4 weeks after starting or increasing an ACE inhibitor or ARB, with timing influenced by current kidney function and potassium. A clinician may arrange earlier testing when risk is higher. Other medications have their own monitoring requirements. KDIGO 2024 CKD guideline executive summary, section 3.6
The examples below illustrate questions to discuss with a clinician. They are not diagnoses or treatment instructions.
| Follow-up pattern | What needs consideration | Useful question |
|---|---|---|
| eGFR is similar, but potassium rises after a medication change | Treatment effects, other exposures, acute illness, and sample quality | How urgently should this be reviewed, and what follow-up is needed? |
| Potassium is flagged and the specimen is reported as hemolyzed | A collection-related elevation is possible, but a true abnormality has not been excluded | Do I need an immediate repeat sample or assessment? |
| CO2 remains low on repeated chemistry tests | A persistent acid-base abnormality and its possible causes | Is this related to CKD, another illness, or a medication? |
| Hemoglobin falls while ferritin and TSAT are low | Iron deficiency may be contributing | What could explain the iron loss or inadequate intake or absorption? |
| Hemoglobin is low, TSAT is low, and ferritin is normal or elevated | Iron availability may be restricted; inflammation and recent treatment matter | Does this represent iron restriction, another anemia mechanism, or both? |
| Hemoglobin falls despite apparently adequate iron findings | Reduced production and other causes still need evaluation | What does the reticulocyte response show, and is further investigation needed? |
Bring the previous report as well as the current one. Two identical flagged values may have different implications when one is longstanding and the other represents a rapid change.
Choose the order around the monitoring question and the clinician's plan. A larger panel is not automatically more useful, particularly when it repeats tests already included elsewhere.
| Testing option | How it may fit a follow-up plan |
|---|---|
| Potassium test | Focused electrolyte follow-up when the other needed chemistry results are already available. |
| Carbon dioxide test | Focused total CO2 measurement when the wider acid-base context is available. |
| Basic metabolic panel or renal function panel | A way to assess several related chemistry measurements together; confirm the ordered panel's components. |
| Complete blood count | Measures hemoglobin and other blood-cell features. |
| Ferritin with iron and total iron-binding capacity | Helps evaluate stored iron and calculate or report TSAT; confirm the panel includes the needed measurements. |
| Reticulocyte count | Adds information about red-cell production when requested as part of anemia evaluation. |
| Vitamin B12 and folate testing | A targeted addition when deficiency is a reasonable concern. |
A chemistry panel does not replace a CBC or iron studies. Likewise, an anemia workup does not replace the urine testing in a CKD monitoring plan. Ask which existing results can be used before repeating a broad collection of tests.
Preparation depends on the complete order. An isolated potassium test generally does not require fasting, while other measurements collected at the same visit may have different instructions. Iron studies may be scheduled in the morning and may require fasting according to the laboratory's directions. MedlinePlus: potassium testing and iron-test preparation
Bring or record:
Follow your usual clinician-directed fluid plan. Do not deliberately overhydrate, fast beyond the instructions, or stop a medication to try to improve a result. During collection, follow the phlebotomist's instructions and avoid repeated fist pumping.
Seek emergency care for chest pain, severe shortness of breath, fainting, or major weakness with a suspected electrolyte problem. A critically abnormal potassium result needs immediate clinical direction even if you feel well. Do not book a routine online retest as a substitute for urgent assessment. National Kidney Foundation: severe hyperkalemia
Sudden breathlessness, chest symptoms, or a rapid deterioration in someone with anemia also requires prompt assessment. NIDDK: when to seek care
For a noncritical abnormal result, contact the clinician responsible for your monitoring plan to establish the timing of review. Symptoms, the speed of change, and accompanying results matter as well as the flagged number.
Yes. A filtration estimate does not directly report potassium balance, acid-base status, or hemoglobin. Those measurements may change for kidney-related or other reasons and need their own interpretation.
No. Potassium is one part of monitoring. It does not replace your kidney-function trend, urine albumin findings, or overall risk assessment.
Total CO2 largely reflects bicarbonate and is commonly used to assess acid-base status. Interpretation still depends on the other results and the clinical situation. MedlinePlus: CO2 blood testing
Not necessarily. The reason for anemia needs evaluation. Iron studies help determine whether iron deficiency or restricted iron availability is contributing; other causes may require a different response. KDIGO 2026 anemia guidance
Ulta Lab Tests can help eligible customers access laboratory testing as part of an established monitoring plan. Before ordering, confirm the requested tests, specimen and preparation requirements, and who will interpret the results. Coordinate with your existing care team to avoid duplicating scheduled testing.
For related education, explore the kidney function testing pillar, the CKD result-interpretation guide, and the CBC and anemia testing pillar.
| Category | Test or panel with embedded link | Role in the article |
|---|---|---|
| Electrolyte monitoring | Potassium Test | Potassium levels and medication-related follow-up |
| Acid-base monitoring | Carbon Dioxide Test | Total CO2 as a bicarbonate-related measurement |
| Chemistry panels | Basic Metabolic Panel | Several related chemistry measurements |
| Chemistry panels | Renal Function Panel | A broader kidney-related chemistry option |
| Anemia evaluation | Complete Blood Count with Differential and Platelets | Hemoglobin, red-cell indices, white cells, and platelets |
| Anemia evaluation | Reticulocyte Count | Newly produced red blood cells and marrow response |
| Iron-status evaluation | Ferritin Test | Iron-storage information |
| Iron-status evaluation | Iron and Total Iron-Binding Capacity Test | Iron studies supporting transferrin saturation assessment |
| Iron-status evaluation | Ferritin, Iron and Total Iron Binding Capacity Panel | Combined iron-study ordering option |
| Conditional nutrient evaluation | Vitamin B12 Test | Targeted evaluation when deficiency is suspected |
| Conditional nutrient evaluation | Folate, Serum Test | Targeted evaluation when folate deficiency is suspected |
| Continuing kidney-function monitoring | Creatinine Test | Creatinine-based filtration assessment; confirm eGFR reporting |
| Continuing urine-albumin monitoring | Albumin Random Urine Test with Creatinine | Urine albumin-to-creatinine ratio assessment |
| Rank | Existing blog category | |
|---|---|---|
| 1 | Kidney → Kidney Health | Primary category |
| 2 | Anemia | Secondary category |
| 3 | Blood Disorders | Optional additional category |
| Priority | Related Health Area | Relevance |
|---|---|---|
| 1 | Kidney Disease Testing | Established CKD and follow-up testing |
| 2 | Renal Function | Kidney-related chemistry monitoring |
| 3 | Anemia Tests | Blood counts, iron status, and anemia evaluation |
| 4 | Kidney Health | Broader kidney-health education |
| 5 | Blood Disorder Tests | Evaluation of blood-cell abnormalities |
Ulta Lab Tests, LLC.
9237 E Via de Ventura, Suite 220
Scottsdale, AZ 85258
480-681-4081
(Toll Free: 800-714-0424)
