Ulta Lab Tests

Hypothyroidism

Hypothyroidism means the thyroid is underactive, producing too little hormone. That can slow metabolism and affect energy, weight, mood, heart rate, fertility, and temperature regulation. The most common cause is Hashimoto thyroiditis (autoimmune). Less often, a pituitary or hypothalamic problem causes central (secondary/tertiary) hypothyroidism.

A proactive approach starts with TSH and Free T4 to confirm a low-thyroid pattern. Thyroid antibodies (TPOAb, ± TgAb) help confirm autoimmunity and inform long-term risk. In selected cases, additional markers (Free T3, lipids, CBC, sodium) and—when indicated—imaging support the evaluation. These tests enable screening, diagnostic triage, and monitoring, but they do not replace a clinician’s exam, imaging for nodules, or urgent care when warning signs appear.

Signs, Symptoms & Related Situations

  • Common symptoms (underactive pattern): fatigue, cold intolerance, weight gain, dry skin/hair loss, constipation, low mood, brain fog

  • Heart & metabolism: slow pulse, high LDL cholesterol, fluid retention

  • Neck clues: goiter (enlarged thyroid), neck fullness, hoarseness, trouble swallowing

  • Women’s health: heavy or irregular periods; trying to conceive or pregnancy/postpartum

  • Medication/exposure flags: amiodarone, lithium, prior neck radiation, iodine contrast, high-dose biotinsupplements (can distort labs)

  • When to seek urgent care (rare but serious): extreme fatigue with confusion, hypothermia, trouble breathing, or very slow heart rate

All symptoms and risks should be reviewed by a qualified clinician.

Why These Tests Matter

What testing can do

  • Confirm hypothyroidism and distinguish overt vs subclinical patterns

  • Identify autoimmune thyroiditis (Hashimoto) with TPO/Tg antibodies

  • Guide monitoring during medication adjustments, pregnancy planning, and long-term follow-up

What testing cannot do

  • Diagnose nodules or cancer by blood test alone—ultrasound/biopsy are clinical decisions

  • Reliably detect thyroid dysfunction in every situation with TSH alone (e.g., central hypothyroidism, late pregnancy)

  • Overcome assay interference (e.g., high-dose biotin) without proper preparation

What These Tests Measure (at a glance)

  • TSH (Thyroid-Stimulating Hormone): first-line screen and treatment monitor; typically elevated in primary hypothyroidism and low/normal in central hypothyroidism.

  • Free T4 (± Free T3): unbound hormones that reflect biologic activity; help grade severity and detect central hypothyroidism (low Free T4 with non-elevated TSH).

  • TPO Antibodies (TPOAb): hallmark of Hashimoto thyroiditis; positivity raises the likelihood of current/future hypothyroidism.

  • Thyroglobulin Antibodies (TgAb): autoimmune context; note that TgAb can interfere with thyroglobulin if cancer surveillance is ever needed.

  • Lipids/CBC/Sodium (context): hypothyroidism can raise LDL-C, contribute to anemia, and rarely lower sodium.

  • Total T4/T3 and TBG (selected): helpful when binding-protein changes (pregnancy, oral estrogen) complicate interpretation.

  • Important prep: Biotin can cause falsely low TSH and falsely high T4/T3—pause 24–48 hours before testing if advised.

Quick Build Guide

Clinical goal Start with Add if needed
Confirm hypothyroidism (symptoms present) TSH • Free T4 TPOAb; lipid panel • CBC for context
Abnormal TSH on routine screen Repeat TSH • Free T4 TPOAb to assess autoimmunity
Possible central hypothyroidism Free T4 • TSH (may be low/normal) Clinician-directed pituitary workup (outside blood tests scope)
Pregnancy or trying to conceive TSH (trimester-aware) • Free T4 TPOAb in selected cases; follow obstetric guidance
Goiter or nodules TSH • Free T4 Clinician-directed ultrasound; antibodies for context
Stable therapy—dose check TSH (± Free T4 on T4 therapy) Cadence per clinician plan
Binding changes (estrogen, pregnancy) TSH • Free T4 Total T4/T3 • TBG if interpretation is unclear

How the Testing Process Works

  1. Pick a starting set: most begin with TSH + Free T4; add TPOAb to confirm autoimmunity.

  2. Prepare for accuracy: list all medicines/supplements; pause high-dose biotin 24–48 hours if advised. Fasting is usually not required.

  3. Provide a sample: standard blood draw.

  4. View secure results: most post within a few days.

  5. Plan next steps: your clinician interprets results with symptoms and exam—and may add ultrasound for nodules/goiter.

Interpreting Results (General Guidance)

  • High TSH + low Free T4 → overt primary hypothyroidism.

  • High TSH + normal Free T4 → subclinical hypothyroidism; risk of progression is higher with positive TPOAb.

  • Low/normal TSH + low Free T4 → consider central hypothyroidism (pituitary/hypothalamic) in the right context.

  • Positive TPOAb (± TgAb) → supports autoimmune cause; antibody level alone does not predict exact severity.

  • Elevated LDL-C or anemia → common companions; trend after clinical changes.
    Lab ranges vary by age, pregnancy, and method. Always interpret results with a qualified healthcare professional.

Choosing Panels vs. Individual Tests

  • Core hypothyroid panel: TSH • Free T4

  • Autoimmune add-ons: TPOAb ± TgAb

  • Special situations: Total T4/T3 • TBG when binding changes are likely; lipids/CBC/sodium for context
    Use bundled panels for efficient screening, then add targeted markers to answer specific questions and track progress.

FAQs

Do I need to fast for thyroid labs?
Usually no. Follow any instructions on your order.

Can supplements affect my results?
Yes—biotin can distort TSH and thyroid hormone results. Share all supplements and medicines before testing.

If my antibodies are positive, do I need treatment right away?
Not always. Antibodies confirm autoimmunity; treatment decisions depend on TSH/Free T4, symptoms, and plans (e.g., pregnancy).

What if I’m pregnant or planning pregnancy?
Your clinician uses trimester-specific ranges and may monitor more closely if you have TPOAb or prior thyroid disease.

Can blood tests detect thyroid cancer?
No. Blood tests assess function and autoimmunity; nodules and cancer are evaluated with ultrasound and, if needed, biopsy.

How often should I recheck labs?
Commonly 6–8 weeks after any medication change, then every 6–12 months when stable—your clinician will set the schedule.

Why might my TSH be normal but I still have symptoms?
Consider central hypothyroidism, binding-protein effects, assay interference, or non-thyroid causes—your clinician will guide next steps.

Related Categories & Key Tests

  • Thyroid Tests Hub

  • All Thyroid Tests • Hashimoto Thyroiditis Tests • Hyperthyroidism & Graves Disease Tests • Thyroid Antibodies • Thyroid in Pregnancy • Thyroid Nodules & Cancer

  • Key Tests: TSH • Free T4 • Free T3 • TPO Antibodies • Thyroglobulin Antibodies • Total T4 • Total T3 • TBG • Lipid Panel • CBC • Sodium

References

  • American Thyroid Association — Guidelines for Hypothyroidism in Adults; Thyroid disease in pregnancy.
  • AACE/ACE — Clinical practice guidelines for hypothyroidism and autoimmune thyroid disease.
  • Endocrine Society — Testing considerations for central hypothyroidism.
  • European Thyroid Association — Subclinical hypothyroidism management statements.
  • AACC/NACB — Laboratory support for thyroid testing; biotin interference advisories.
  • Clinical reviews on interpreting TSH/Free T4 patterns and antibody positivity in Hashimoto thyroiditis.

Available Tests & Panels

Your Hypothyroidism Tests menu is pre-populated in the Ulta Lab Tests system. Start with the core panel (TSH, Free T4), then use filters to add TPO/Tg antibodies for autoimmune context and lipids/CBC to assess common companions. Add Total T4/T3/TBG when binding changes are likely. Follow any preparation guidance—especially pausing high-dose biotin if advised—and review results with your clinician to confirm findings and plan monitoring.

How to Test for Hypothyroidism: 18 Key Lab Tests

Did you know that an estimated 20 million Americans have some form of thyroid disease?

Among the different types of thyroid disorders, hypothyroidism is the most common. Most of the time, hypothyroidism is mild and causes few (if any) major symptoms.

Left untreated, however, it can worsen over time and lead to other complications with your health.

Is there a history of thyroid disease in your family? Have you noticed symptoms of hypothyroidism in your body? Are you wondering how to test for hypothyroidism?

In this post, we'll briefly discuss some common hypothyroidism symptoms and risk factors. Then we'll reveal 18 different lab tests you can order to test for hypothyroidism.

Read on to learn more—your health depends on it!

What Is Hypothyroidism?

Before we dive into screening and testing, let's first define hypothyroidism.

Your thyroid is a butterfly-shaped gland located in your throat. As one of your body's endocrine glands, it's responsible for producing certain hormones.

Among other functions, your thyroid regulates your metabolism, your heart rate, and your body temperature. If your thyroid isn't active enough to produce the hormones your body needs, these functions will begin to slow down.

When this happens, it's known as hypothyroidism (underactive thyroid).

Hypothyroidism Symptoms

The symptoms of hypothyroidism vary depending on the severity of the hormonal deficiency. Problems tend to develop very slowly, usually over a number of years.

At first, you may hardly notice the symptoms of hypothyroidism. You may attribute symptoms like fatigue and weight gain to getting older.

But as your metabolism continues to slow down, you may soon develop more obvious problems. Hypothyroidism signs and symptoms may include:

  • Fatigue
  • Increased sensitivity to cold
  • Constipation
  • Dry skin
  • Weight gain
  • Puffy face
  • Hoarseness
  • Muscle weakness
  • Elevated blood cholesterol level
  • Muscle aches, tenderness, and stiffness
  • Pain, stiffness, or swelling in your joints
  • Heavier or irregular menstrual periods
  • Thinning hair
  • Slowed heart rate
  • Depression
  • Impaired memory
  • Enlarged thyroid gland (goiter)

Children and teens who develop hypothyroidism generally have the same symptoms as adults. But they may also experience:

  • Poor growth, resulting in short stature
  • Delayed development of permanent teeth
  • Delayed puberty
  • Poor mental development

These symptoms are often vague and don't outwardly appear to be related. If you notice some of these symptoms over an extended period of time, it's a good idea to get tested.

The sooner you do, the sooner you can get diagnosed and receive the treatment you need.

Risk Factors for Hypothyroidism

Although anyone can develop hypothyroidism, you're at an increased risk if you:

  • Are a woman
  • Are older than 60
  • Have a family history of thyroid disease
  • Have an autoimmune disease, such as type 1 diabetes or celiac disease
  • Have been treated with radioactive iodine or anti-thyroid medications
  • Received radiation to your neck or upper chest
  • Have had thyroid surgery (partial thyroidectomy)
  • Have been pregnant or delivered a baby within the past six months

Keep in mind that these are generalizations and that hypothyroidism can affect anyone of any age.

How to Test for Hypothyroidism: 18 Key Lab Tests

Now that you understand hypothyroidism symptoms and risk factors, how do you test for it?

It will likely require a combination of tests to determine your hormone levels and other factors that indicate a thyroid disorder. To make things easier, here's a list of 18 tests you can order to measure how active (or underactive) your thyroid may be.

1. TSH

TSH stands for "thyroid-stimulating hormone." This is the first place to start when you're evaluating the health of your thyroid.

TSH is produced in your pituitary gland inside your brain. This is the "master gland" that controls the level of hormones your thyroid produces and releases into your body.

This test measures how much TSH is in your bloodstream. Normal levels are anywhere between 0.4 and 4.0 milliunits per liter (mU/L). If your TSH levels are too high (over 4.0), it means your thyroid is underactive and could be a sign of hypothyroidism.

2. T3 Reverse, LC/MS/MS

Your body uses part of the T4 thyroid hormone to produce Reverse T3 (rT3). This serves as an inactive form of thyroid hormone.

Reverse T3 may attach to the Free T3 receptors, which slows down your metabolic processes. Some studies suggest that high levels of rT3 can contribute to acute major depressive disorder.

Ordering a Reverse T3 test can help you determine if your body is effectively converting T4 into the proper amount of Free T3 and rT3. Normal levels are below 250 pg/ml (10 to 24 ng/dL).

3. T3 Total

This test measures blood levels of the thyroid hormone T3 (triiodothyronine). Some T3 is directly produced in the thyroid gland, but most T3 is the result of chemical conversion from T4.

Bound T3 attaches to hormones that help to transport it throughout the body. Free T3 circulates through the bloodstream unattached.

A T3 total test measures both the bound and free types of T3 in your body. A normal result range is 100-200 nanograms per deciliter (ng/dL).

4. T3, Free

As mentioned above, there are two types of T3 inside your body. Total T3 may be affected by protein levels and your body's protein binding ability, but the Free T3 hormone is not.

While a Total T3 test measures both types, this test only measures your Free T3 levels. Either test (Free T3 or Total T3) can be used to assess your current hormone levels. The normal range is for Free T3 is 260-480 pg/dL or 4-7.4 pmol/L.

Keep in mind that any of these tests on their own won't be enough to make a diagnosis. By studying your TSH, T4, and T3 levels, your doctor will be able to determine if you have hypothyroidism.

5. T4 (Thyroxine), Total

T4 is the main thyroid hormone your body produces. Also called thyroxine, it plays an important part in regulating your weight, body temperature, metabolism, and mood.

In a healthy thyroid, some T4 also converts into T3 to be used by the body. If you have hypothyroidism, this process can be interrupted. A high TSH level combined with low levels of T4 may signal hypothyroidism.

A Total T4 test is an essential part of assessing and diagnosing an underactive thyroid.

6. T4 Free (FT4)

Approximately 99% of T4 hormones are bound. This means they're attached to proteins that prevent them from entering the body's tissues.

Since most T4 is converted into T3, Free T4 is the more important hormone to measure. Any changes the could indicate hypothyroidism will show up first in T4.

The normal range for Free T4 is 0.8 to 2.8 nanograms per deciliter (ng/dL). You can find out your levels with a T4 Free test.

7. Thyroglobulin Antibodies (TgAb)

One of the most common causes of hypothyroidism is an autoimmune disease known as Hashimoto's.

With Hashimoto's, your body mistakes your healthy, functioning thyroid for a "foreign" invader. It then launches an attack against the thyroid in the form of antibodies.

If you're healthy and your thyroid is functioning normally, you'll have no measurable amount of TgAb in your blood. Elevated levels in a TgAb test are a possible sign of an autoimmune version of hypothyroidism.

8. Thyroid Peroxidase Antibodies (TPO)

Thyroid peroxidase (TPO) is an enzyme found in your thyroid gland. It plays an important role in the normal production of thyroid hormones.

Similar to the thyroglobulin antibodies, there's no reason for your body to produce antibodies against this enzyme. The presence of TPO antibodies in your blood signals an autoimmune attack on your thyroid.

A TPO test detects the level of antibodies against TPO in the blood. The normal range is 0-35 IU/mL.

9. TRAb (TSH Receptor Binding Antibody)

TRAb is an antibody to the thyroid cell receptor for thyroid-stimulating hormone (TSH).

It's found in most patients with Graves' Disease and is a primary cause of hyperthyroidism (overactive thyroid). Normal levels fall between 0.0−1.75 units/L.

What if you have some symptoms that seem hyper and some that seem hypo? This test can help rule out hyperthyroidism and bring you one step closer to the right diagnosis.

10. TSI (Thyroid Stimulating Immunoglobulin)

TSI stands for thyroid-stimulating immunoglobulin. It signals the thyroid gland to swell and release excessive amounts of thyroid hormone into the bloodstream.

TSIs mimic the action of TSH, causing over-secretion of T3 and T4. The TSI level will be abnormally high in persons with hyperthyroidism (Grave's Disease). Normal levels are less than 1.3 or 130%.

A TSI test will measure this hormone in your blood and help your doctor assess your thyroid function.

11. CBC (includes Differential and Platelets)

CBC stands for complete blood count. It's the most commonly ordered blood test to evaluate your overall health.

This test measures the cells that make up your blood, including red and white blood cells as well as hemoglobin, hematocrit, and platelets. Abnormally high or low levels of any of these components can signal an underlying medical condition.

Be sure to include a CBC test with any specific thyroid tests you order. This will provide your doctor with "the whole picture" of what's going on inside your body.

12. Comprehensive Metabolic Panel (CMP)

One of the main symptoms of hypothyroidism is a sluggish metabolism. A CMP test provides vital information about your body's metabolism and chemical balance.

This test measures glucose, electrolytes, calcium, and protein levels in your blood. Like abnormalities in the CBC test, unusually high or low results means your body isn't performing at an optimal level.

The results of this common test can help your doctor determine how fast or slow your metabolism is functioning.

13. Hemoglobin A1c (HgbA1C)

This hemoglobin A1c test reveals your average blood sugar levels over the past few months. It's commonly ordered to help diagnose diabetes.

What does this have to do with thyroid function? Both diseases indicate dysfunction within the endocrine system. Research has found that thyroid disorders can have a major impact on glucose control.

Ordering a HgbA1C test will let you know if your blood sugar is within the normal limits (between 4%-5.6%)

14. Iron and Total Iron Binding Capacity (TIBC)

Diabetes isn't the only disease linked with hypothyroidism.

Anemia is a frequently occurring clinical condition that accompanies thyroid disease. In fact, prolonged iron deficiency can contribute to the development of hypothyroidism.

The TIBC test measures the amount of iron that would appear in blood if all the transferrin were saturated with iron. This reveals if you're anemic, which could facilitate a diagnosis.

15. Lipid Panel with Ratios

Hypothyroidism can contribute to elevated cholesterol levels.

When your body isn't producing enough thyroid hormones, it doesn't have the tools it needs to efficiently break down and remove cholesterol.

A lipid panel test will measure your body's levels of "good" cholesterol (HDL), as well as the "bad" cholesterol (LDL). Higher than normal levels (less than 200 milligrams per deciliter) could signal an underlying thyroid problem.

16. Vitamin D 25-Hydroxyvitamin D (D2, D3)

Hypothyroidism can impair your body's ability to absorb certain vitamins, like Vitamin D.

Over time, low levels of Vitamin D can affect your heart and your bones, reducing your overall bone density.

Check your levels with this Vitamin D test to ensure your levels are where they should be. If they're too low (less than 12 ng/mL), you're Vitamin D deficient and could have hypothyroidism.

17. Vitamin B12 (Cobalamin)

Your B-vitamin levels are another way to determine how well your body is functioning.

In the case of people with hypothyroidism, a Vitamin B12 deficiency often results from gradual damage to the digestive tract. This prevents the absorption of vital nutrients like B-vitamins, which are essential to your wellbeing.

A Vitamin B12 test will reveal if you're within the normal range (200-900 nanograms per milliliter (ng/mL).

18. Vitamin B6 (Pyridoxal Phosphate)

A final test you can take for hypothyroidism is Vitamin B6.

B6 is essential for your body's protein, fat, and carbohydrate metabolism. It also aids in the creation of red blood cells and neurotransmitters.

If you have an underactive thyroid, your body won't absorb B6 as efficiently as it should. This test will determine if your Vitamin B6 levels are normal (5-50 micrograms per liter).

Symptoms of Hypothyroidism? Order Your Tests Today

Hypothyroidism is a common condition with many treatment options available. But first, you have to get diagnosed.

Are you noticing hypothyroidism symptoms? Is there a history of hypothyroidism or other autoimmune diseases in your family? Or do you just feel like something is "off" and you can't quite figure out what it is?

If you answered "Yes" to any of these questions, it's time to take action. Before you can seek hypothyroidism treatment, you need to find out exactly what's happening inside your body.

Keep in mind that test results alone can't prove or diagnose any condition, including hypothyroidism. You'll need to review your results with your doctor before you can receive an official diagnosis and treatment plan.

Now that you know how to test for hypothyroidism, the only thing left to do is get started.

Click here to view our most popular thyroid health panels and take the first step towards a healthier you.