---
title: "Vitamin D test (25-hydroxy): what it measures, normal levels, and who should be tested"
type: biomarker
url: "https://www.test-well.com/biomarkers/vitamin-d-25-hydroxy"
also_known_as:
  - vitamin d
  - 25-hydroxy vitamin d
  - vitamin d, 25-hydroxy
  - 25-oh vitamin d
  - 25(oh) vitamin d
  - vitamin d, 25-oh
category: Vitamins & Nutrients
units:
  - ng/mL
order_price_usd: 41.99
order_item: Vitamin D, 25-Hydroxy
order_url: "https://www.test-well.com/tests/vitamin-d"
reviewed_at: 2026-09-17
---

# Vitamin D test (25-hydroxy): what it measures, normal levels, and who should be tested

> Vitamin D, 25-Hydroxy is measured with a standard blood draw; no fasting is needed. A typical reference range is 30.0 – 100 ng/mL. At TestWell it's $41.99 all-in as Vitamin D, 25-Hydroxy, results in 1–3 business days, drawn at Quest or Labcorp. An out-of-range result is a prompt to look closer, not a diagnosis.

The vitamin D test measures 25-hydroxyvitamin D, the storage form that reflects what you have taken in from sun, food and supplements over the past few weeks. It is the only test that shows vitamin D status. Most labs call 30–100 ng/mL normal, below 20 ng/mL deficient, and 20–29 ng/mL insufficient; no fasting is needed and results take a few business days.

Also known as: vitamin d, 25-hydroxy vitamin d, vitamin d, 25-hydroxy, 25-oh vitamin d, 25(oh) vitamin d, vitamin d, 25-oh.

## Key facts

| Fact | Value |
| --- | --- |
| Units | ng/mL |
| Sample | Blood draw |
| Fasting | Not required |
| Results | 1–3 business days |
| Price | $41.99 |
| Labs | Quest or Labcorp · BioReference in NY/NJ |

## What does a vitamin D test measure?

Vitamin D arrives two ways: your skin makes vitamin D3 from UVB sunlight, and you take in D3 from animal foods and most supplements and D2 from fortified foods, some mushrooms and prescription D2. The liver converts both into 25-hydroxyvitamin D, which circulates for two to three weeks and is the form the body draws on. The kidneys then activate a small amount into 1,25-dihydroxyvitamin D, the hormone that actually raises calcium absorption.

The standard test measures total 25-hydroxyvitamin D (D2 plus D3). It is the right test for status because it has a long half-life and tracks intake; 1,25-dihydroxyvitamin D is tightly regulated, stays normal or even rises in deficiency, and is only ordered for specific kidney, parathyroid and granulomatous conditions. Results are reported in nanograms per milliliter (ng/mL) in the US and nanomoles per liter (nmol/L) elsewhere; multiply ng/mL by 2.5 to convert.

## Who should get a vitamin D test?

The Endocrine Society's 2024 guideline recommends against routine vitamin D testing in generally healthy adults, because the evidence does not show that testing and treating people without risk factors improves outcomes. Testing is aimed instead at people whose result would change what they do: those with osteoporosis or an unexplained fracture, bone pain or muscle weakness, or a condition that impairs absorption or metabolism.

The groups most likely to have a low level — and the usual reasons a clinician orders the test — are people with celiac disease, Crohn's disease, cystic fibrosis or previous bariatric surgery; chronic kidney or liver disease; obesity; darker skin; very limited sun exposure from indoor work, covering clothing or northern latitude; older adults, especially with falls or fractures; people on anticonvulsants, glucocorticoids, certain HIV medications or long-term antifungal therapy; and anyone with an abnormal calcium, phosphorus, alkaline phosphatase or parathyroid hormone result.

The other common reason to test is follow-up: confirming that a previously low level has responded after about three months of supplementation, or checking that a high-dose regimen has not overshot.

## How to get a vitamin D test and prepare for it

The test is a routine blood draw with no fasting and no time-of-day requirement. You can order it online through TestWell — a licensed physician reviews the order, you visit a nearby Quest or Labcorp patient service center, and results arrive in your portal, typically within a few business days — or have your own clinician order it. It is commonly bundled into wellness, vitamin-deficiency and bone-health panels.

Two things affect interpretation. Season: levels bottom out in late winter and peak in late summer, so a February result is close to your personal low and an August result close to your high. Supplements: 25-hydroxyvitamin D takes roughly three months to plateau after a change in dose, so testing a few weeks into a new supplement shows a level still climbing. If you have recently taken a very large single dose, mention it, because it can raise the level temporarily. Ordinary daily supplements do not need to be stopped before the draw.

## What is the normal range for Vitamin D, 25-Hydroxy?

| Population | Reference range |
| --- | --- |
| age 18+ | 30.0 – 100 ng/mL |

Reference intervals differ slightly between labs; the range printed on your report is the one to interpret against. Ranges are usually set so 95% of healthy people fall inside them.

## Normal vitamin D levels: deficient, insufficient, sufficient and high

Two expert bodies have drawn the lines in slightly different places, which explains why you may see 20 ng/mL in one article and 30 ng/mL in another. The Institute of Medicine (now the National Academies) concluded in 2011 that 20 ng/mL (50 nmol/L) covers the bone-health needs of at least 97.5% of the population. The Endocrine Society's 2011 clinical guideline set deficiency below 20 ng/mL, insufficiency at 21–29 ng/mL and sufficiency at 30 ng/mL and above, and most US laboratories, including Quest and Labcorp, print 30–100 ng/mL as the reference range.

Below about 12 ng/mL the risk of rickets in children and osteomalacia in adults rises clearly, and that is where nearly everyone agrees treatment is needed. Levels above 100 ng/mL are flagged as potentially toxic, though symptoms of toxicity — driven by high calcium — usually appear well above 150 ng/mL and almost always come from very high supplement doses rather than sun or food.

| Category | ng/mL | nmol/L | What it usually means |
| --- | --- | --- | --- |
| Severely deficient | below 12 | below 30 | Risk of osteomalacia / rickets; treatment generally recommended |
| Deficient | 12–19 | 30–49 | Below the level most guidelines consider adequate |
| Insufficient | 20–29 | 50–74 | Adequate for most by IOM criteria; below the Endocrine Society target |
| Sufficient | 30–100 | 75–250 | The reference range printed on most US lab reports |
| High | above 100 | above 250 | Flagged; toxicity risk rises with calcium, usually from over-supplementation |

_Multiply ng/mL by 2.5 to convert to nmol/L. Thresholds from the Endocrine Society and the Institute of Medicine._

## What drives your vitamin D level up or down

Sunlight is the largest input for most people, and everything that limits UVB — latitude, season, time indoors, clothing, sunscreen, air pollution and darker skin, which needs longer exposure to make the same amount — lowers the level. Diet contributes less than people expect; few foods contain much vitamin D naturally, and fortified milk, cereals and fatty fish are the main sources.

Body composition matters: vitamin D is stored in fat, so people with obesity have lower circulating levels for the same intake and often need more to reach a target. Fat malabsorption from celiac disease, Crohn's disease, pancreatic insufficiency or bariatric surgery reduces absorption from food and supplements alike. Kidney and liver disease impair the conversion steps, and medications that speed up liver metabolism — some anticonvulsants, glucocorticoids and rifampin — break down vitamin D faster. Genetic differences in the vitamin D binding protein also shift measured totals between individuals and ancestries.

## Tests read alongside vitamin D

Vitamin D does not act alone, and a low or high result is usually interpreted with calcium, phosphorus, alkaline phosphatase and parathyroid hormone (PTH). Long-standing deficiency raises PTH as the body fights to hold calcium steady; a high vitamin D with a high calcium suggests over-supplementation; a high calcium with a low PTH and a normal 25-hydroxy level points elsewhere. Kidney function (creatinine, eGFR) matters because the kidneys perform the final activation step.

The 1,25-dihydroxyvitamin D test is reserved for specific situations — suspected sarcoidosis or other granulomatous disease, certain lymphomas, inherited disorders of vitamin D metabolism and advanced kidney disease — and is not a substitute for the 25-hydroxy test when the question is simply whether your stores are adequate.

## What happens after a low or high vitamin D result

A low result usually leads to supplementation, with the dose and form chosen by a clinician based on how low the level is, body weight, absorption and other conditions — it is not one-size-fits-all, and very high doses carry their own risks. Because the level takes about three months to plateau, a follow-up test around then confirms the response; once in range, many people recheck yearly, often in late winter.

A high result prompts a review of every supplement and fortified product you take and a calcium check; the interpretation sections below go through the causes, symptoms and next steps for both directions. Bone density testing, a celiac screen or a broader malabsorption work-up follows when the low level is severe, recurrent or unexplained.

## What does a high Vitamin D, 25-Hydroxy mean?

High 25-hydroxyvitamin D almost always comes from supplements, particularly high-dose products or loading doses. Levels above about 50 ng/mL add no benefit; toxicity — high calcium, nausea, kidney stones, confusion — is generally seen above 100–150 ng/mL with prolonged intake. Sunlight alone does not produce toxic levels. The next step is checking calcium and reviewing the dose.

### Common causes of high Vitamin D, 25-Hydroxy

1. High-dose supplements or a recent 50,000 IU loading course
2. Combination products (multivitamin plus separate D plus fortified foods)
3. Rare: granulomatous diseases or lymphoma (affect the active form)
4. Biotin interference on some assays

### Symptoms that go with high Vitamin D, 25-Hydroxy

- Usually none below 100 ng/mL
- Nausea, constipation, excessive thirst and urination, confusion when toxic

### What clinicians usually check next

- Serum calcium and a metabolic panel
- Review every supplement and fortified food
- Repeat after 2–3 months on a lower dose

Follow-up tests at TestWell: [Calcium](https://www.test-well.com/tests/calcium) ($26.99).

**Is 80 ng/mL vitamin D too high?** It's above what's needed and above most labs' reference range, though below the levels linked to toxicity. Most clinicians would lower the dose and recheck calcium.

## What does a low Vitamin D, 25-Hydroxy mean?

Low vitamin D is very common — limited sun exposure, darker skin, northern latitude, indoor work, obesity, malabsorption and older age all lower 25-hydroxyvitamin D. The NIH considers below 12 ng/mL deficient and 12–20 ng/mL inadequate; many clinicians aim for 30 ng/mL or more. Replacement is straightforward; retest 8–12 weeks after starting to confirm the dose works.

### Common causes of low Vitamin D, 25-Hydroxy

1. Little sun exposure: winter, indoor work, sunscreen, covering clothing
2. Darker skin (less D synthesis per unit of sun)
3. Obesity (vitamin D is sequestered in fat)
4. Malabsorption: celiac disease, Crohn's, bariatric surgery
5. Kidney or liver disease; some anticonvulsants and glucocorticoids

### Symptoms that go with low Vitamin D, 25-Hydroxy

- Often none
- Bone and muscle aches, proximal weakness
- Fatigue, low mood
- Fractures or bone softening when severe and prolonged

### What clinicians usually check next

- Calcium, phosphorus and PTH if very low or if bone symptoms are present
- Consider celiac screening when there's no obvious reason
- Retest 25-hydroxyvitamin D 8–12 weeks after starting supplementation

Follow-up tests at TestWell: [Calcium](https://www.test-well.com/tests/calcium) ($26.99), [PTH (Parathyroid Hormone)](https://www.test-well.com/tests/parathyroid-hormone-test) ($59.99), [Phosphorus](https://www.test-well.com/tests/phosphorus-test) ($18.99).

**What vitamin D level is deficient?** Below 12 ng/mL is deficient and 12–20 ng/mL inadequate by NIH criteria; the Endocrine Society and many labs flag below 20 or 30 ng/mL as low.

**How long until my level rises?** 25-hydroxyvitamin D has a two-to-three-week half-life, so the new steady state takes about two to three months. Retest at 8–12 weeks.

## How often should you retest?

If you're correcting a low level, retest about 3 months after starting supplementation — that's roughly how long 25-hydroxyvitamin D takes to plateau on a steady dose, per the Endocrine Society's deficiency guideline. Once in range, many people recheck annually, often in late winter when levels are lowest.

## How do you get tested for Vitamin D, 25-Hydroxy?

| Order | Type | Price | Includes |
| --- | --- | --- | --- |
| [Vitamin D, 25-Hydroxy](https://www.test-well.com/tests/vitamin-d) | Single test | $41.99 | This marker |
| [Basic Vitamin Deficiency Panel](https://www.test-well.com/tests/vitamin-deficiency-panel) | Panel | $89.99 | 3 tests |
| [Post-COVID Recovery Panel](https://www.test-well.com/tests/post-covid-panel) | Panel | $99.99 | 7 tests |
| [Metabolism & Weight Loss Panel](https://www.test-well.com/tests/metabolism-panel) | Panel | $119.99 | 8 tests |
| [Fitness & Performance Panel](https://www.test-well.com/tests/fitness-performance-panel) | Panel | $119.99 | 8 tests |

## Quest vs Labcorp vs BioReference

| Lab | Available | Price | Notes |
| --- | --- | --- | --- |
| Quest Diagnostics | Yes | $41.99 | Choose Quest at checkout; walk-in patient service centers in every state TestWell serves outside NY and NJ. |
| Labcorp | Yes | $41.99 | Choose Labcorp at checkout; walk-in patient service centers in every state TestWell serves outside NY and NJ. |
| BioReference (NY & NJ) | Yes | $44.99 | New York and New Jersey orders route here automatically — state rules keep Quest and Labcorp from accepting self-ordered draws. |

## Common questions about Vitamin D, 25-Hydroxy

### What is a normal vitamin D level?

Most US labs report 30–100 ng/mL as the normal range for 25-hydroxyvitamin D. Below 20 ng/mL is deficient, 20–29 ng/mL is insufficient by Endocrine Society criteria (though adequate for many people by Institute of Medicine criteria), and above 100 ng/mL is flagged as high.

### Do I need to fast for a vitamin D test?

No. The test can be done at any time of day with no preparation. Keep taking a usual daily supplement; just mention any recent very large dose, and remember a new supplement takes about three months to show its full effect.

### How long does it take for vitamin D levels to go up?

About three months on a steady dose, which is when the level plateaus and a retest is meaningful. Testing a few weeks in shows a level that is still rising.

### What is the difference between 25-hydroxy and 1,25-dihydroxy vitamin D?

25-hydroxy is the storage form and the standard test for status. 1,25-dihydroxy is the active hormone, tightly regulated by the kidneys and parathyroid; it stays normal in ordinary deficiency and is only ordered for specific kidney, parathyroid and granulomatous conditions.

### Can you have too much vitamin D?

Yes, almost always from supplements rather than sun. Levels above 100 ng/mL are flagged, and toxicity — nausea, weakness, kidney stones and confusion from high blood calcium — usually appears above 150 ng/mL after months of very high-dose use.

### Should everyone get their vitamin D checked every year?

Current Endocrine Society guidance does not recommend routine testing in healthy adults without risk factors. Testing makes sense when you have a condition, medication or exposure pattern that lowers vitamin D, symptoms or bone problems, or a previous low level being corrected.

### Do I need a doctor's order to test my vitamin d, 25-hydroxy?

No. TestWell's licensed physician network reviews and approves your order — usually within minutes. You can place an order online without an in-person visit or a referral from your own doctor.

### How long does it take to get Vitamin D, 25-Hydroxy results?

Most Vitamin D, 25-Hydroxy results are available in 1–3 business days after your specimen arrives at the lab. You'll get an email the moment your results are ready, with everything viewable in your TestWell portal.

### How much does a Vitamin D, 25-Hydroxy test cost?

Our Vitamin D, 25-Hydroxy starts at $41.99. That's the all-in price — no copays, no insurance hoops, no surprise bills. HSA and FSA cards are accepted.

### Do I need to fast before my Vitamin D, 25-Hydroxy test?

Fasting is not required for the Vitamin D, 25-Hydroxy test. You can have your blood drawn any time of day.

### Which lab will process my Vitamin D, 25-Hydroxy test?

Your test will be processed by Quest Diagnostics, Labcorp, or BioReference depending on which is closest to you and which lab carries the test. All three are CLIA-certified and trusted by hospitals nationwide. You'll choose your lab during checkout from 4,000+ locations.

## Keep reading

- [Blood Tests to Get at 40](https://www.test-well.com/guides/blood-tests-at-40)
- [Blood Tests for Women's Health](https://www.test-well.com/guides/blood-tests-for-womens-health)
- [Fatigue: which blood tests?](https://www.test-well.com/symptoms/fatigue)
- [Muscle weakness: which blood tests?](https://www.test-well.com/symptoms/muscle-weakness)
- [Joint pain: which blood tests?](https://www.test-well.com/symptoms/joint-pain)
- [Hair loss: which blood tests?](https://www.test-well.com/symptoms/hair-loss)
- [Low libido: which blood tests?](https://www.test-well.com/symptoms/low-libido)
- [Mood swings and irritability: which blood tests?](https://www.test-well.com/symptoms/mood-swings)
- [Before your test: Vitamin D supplements](https://www.test-well.com/prep/vitamin-d-supplements)

## Sources

- [Endocrine Society](https://www.endocrine.org/clinical-practice-guidelines/vitamin-d-deficiency)
- [Endocrine Society — Evaluation, Treatment, and Prevention of Vitamin D Deficiency (2011)](https://doi.org/10.1210/jc.2011-0385)
- [Endocrine Society — Vitamin D for the Prevention of Disease (2024 guideline)](https://doi.org/10.1210/clinem/dgae290)
- [NIH Office of Dietary Supplements — Vitamin D Fact Sheet for Health Professionals](https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/)
- [Institute of Medicine — Dietary Reference Intakes for Calcium and Vitamin D (2011)](https://doi.org/10.17226/13050)

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- [Vitamin B12](https://www.test-well.com/biomarkers/vitamin-b12)
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- [Reference range lookup tool](https://www.test-well.com/tools/reference-range-lookup)
- [Lab unit converter](https://www.test-well.com/tools/lab-unit-converter)
- [All biomarkers](https://www.test-well.com/biomarkers)

---

Medically reviewed by Youmna DiStefano, MD (Medical Reviewer, TestWell); last reviewed 2026-09-17. Review policy: https://www.test-well.com/reviewers/youmna-distefano-md

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