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Nutrients

Vitamin D

Also known as: 25-hydroxyvitamin D test, 25(OH)D test, Calcidiol test, Vitamin D₂ and D₃ test

A vitamin D test measures how much 25-hydroxyvitamin D is in your blood — the main form of vitamin D circulating in your body. Vitamin D helps you absorb calcium and phosphorus, supporting strong bones, healthy teeth, and normal muscle and nerve function.

Providers may order this test if you have symptoms or risk factors for deficiency, such as fatigue, bone pain, or frequent illness. It’s also used to monitor conditions like osteoporosis, malabsorption, or kidney disease.

With telehealth, a provider can review your symptoms, order lab work, and interpret results. If your vitamin D level is too low or too high, a healthcare provider can determine whether it’s safe to manage remotely — for example, through supplements or diet changes — or if in-person care is needed.

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Key takeaways

  • Sample required: Blood (serum)

  • Tests for: Vitamin D status, which can help evaluate bone health, calcium balance, and certain metabolic or immune conditions

  • Healthy range: Typically 20–100 nanograms per milliliter (ng/mL)

What can a vitamin D test tell you?

A vitamin D test helps your provider:

  • Check bone and muscle health. Low levels can cause bone pain, muscle weakness, or fractures.

  • Evaluate calcium balance. Vitamin D works with calcium and parathyroid hormone to keep blood calcium steady.

  • Monitor chronic illness. It’s useful to know the vitamin D status of people with osteoporosis, kidney disease, or certain autoimmune conditions.

  • Track supplement response. Testing can reveal whether vitamin D therapy is improving levels.

The U.S. Preventive Services Task Force (USPSTF) does not recommend routine screening in adults without symptoms, noting insufficient evidence that population-wide testing improves health outcomes.

What is being tested?

This test measures 25-hydroxyvitamin D, the storage form of vitamin D in the blood. The levels tested include:

  • Vitamin D₂ (ergocalciferol). From plant foods and supplements.

  • Vitamin D₃ (cholecalciferol). Made in the skin from sunlight and found in animal foods and supplements.

The liver converts vitamin D from sunlight or diet into 25-hydroxyvitamin D, which is then converted by the kidneys into 1,25-dihydroxyvitamin D (calcitriol) — the active form that helps regulate calcium and phosphate. Because 25-hydroxyvitamin D stays in the bloodstream longer, it’s the best indicator of vitamin D status.

Where is the vitamin D test typically included?

Most commonly, providers order vitamin D as an individual test to evaluate deficiency or monitor supplementation. The test measures total 25-hydroxyvitamin D (the sum of D₂ and D₃).

In some cases, it’s included alongside other labs — such as calcium, phosphorus, or parathyroid hormone — when assessing bone health or as part of diagnostic testing for kidney disease or metabolic disorders. It’s not automatically part of standard panels like the basic metabolic panel (BMP) or comprehensive metabolic panel (CMP).

Who should get a vitamin D test?

Testing may be recommended if you have symptoms or risk factors such as:

Symptoms:
Risk factors:

  • Limited sun exposure (northern climates, indoor lifestyle, sunscreen use)

  • Darker skin tone

  • Older age

  • Obesity

  • Digestive disorders (celiac disease, Crohn’s, ulcerative colitis)

  • Chronic kidney or liver disease

  • Long-term use of certain medications (glucocorticoids, anticonvulsants)

Providers also monitor vitamin D in people being treated for osteoporosis, osteomalacia, or parathyroid disorders, or anyone taking high-dose supplements.

How Labs by Hims works

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Not available in all 50 states. Eligibility and provider order required. Lab results alone are not intended to diagnose, treat, or cure any condition. A provider will reach out about critical results and plans include access to 24/7 provider messaging.

Images for illustrative purposes only.

Frequently asked questions

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What causes changes in vitamin D levels?

Vitamin D levels can fluctuate for several reasons related to sunlight exposure, diet, health conditions, and medication use. Low levels (deficiency) are often linked to limited time in the sun, low intake of vitamin D–rich foods, or conditions that reduce absorption, such as certain digestive disorders. Chronic kidney or liver disease, obesity, and medications like glucocorticoids, anticonvulsants, or some HIV treatments can also lower vitamin D. 

Conversely, high levels (excess) are less common but may result from taking too many supplements, consuming large amounts of fortified foods, or from rare medical conditions such as sarcoidosis or lymphoma, which can increase the body’s production of active vitamin D.

What is a normal range for vitamin D?

A healthy range for vitamin D is typically 20–100 nanograms per milliliter (ng/mL), though exact ranges vary by lab.

Can this test be done at home?

Yes. Some at-home kits use a small finger-prick sample mailed to a lab, though clinic tests are usually more precise.

What are the screening recommendations for vitamin D?

Testing is generally recommended for people at risk of deficiency — including those with limited sun exposure, darker skin tones, malabsorption disorders, or chronic kidney disease.

Do I need to fast before the test?

No fasting is required, but you may be asked to skip supplements the day before.

How long do results take?

Most labs report results within one to three business days.

How often should I get tested?

If your levels are normal and you don’t have risk factors, testing every few years is enough. People taking supplements or experiencing chronic illness may need checks every 6–12 months.

Does insurance cover it?

Usually, yes, when ordered for a medical reason such as bone disease or deficiency symptoms. However, insurance is not required for lab testing through Hims.

What happens if I don’t treat low vitamin D?

Untreated deficiency can weaken bones (osteomalacia or osteoporosis), raise fracture risk, and cause muscle weakness or fatigue.

Can I get enough vitamin D from sunlight alone?

It depends on location, skin tone, and time spent outdoors. Many people in northern climates or with darker skin require supplements or fortified foods.

What tests are related to this biomarker?

• Calcium and phosphorus tests

• Parathyroid hormone (PTH) test

• Comprehensive metabolic panel (CMP)

• Bone density (DEXA) scan

• Kidney and liver function tests

The information provided here is for informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always talk to a qualified healthcare provider about your specific health concerns.

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Reviewed by Lynn Marie Morski, MD

Published 11/19/2025