Vitamin D (25-Hydroxy)
The main form of vitamin D circulating in your blood, and the standard way to check your vitamin D status.
AI-verified against cited sources. Awaiting expert reviewAlso called 25(OH)D, 25-OHD, VitDLOINC 62292-8
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What it is
Your skin makes vitamin D from sunlight, and you also get it from food and supplements. The liver converts it into 25-hydroxyvitamin D, which stays in the blood for weeks, so this test reflects your supply over the past couple of months. The body later turns a small amount into the active hormone that helps you absorb calcium.
Why it matters
Vitamin D helps your gut absorb calcium and phosphorus, which keeps bones strong. Very low levels can cause soft or weak bones (rickets in children, osteomalacia in adults). Low levels are also linked to many other conditions, but large trials have mostly not shown that supplements prevent them in people who aren't deficient.
If it’s low
A low level means your body may not have enough vitamin D to absorb calcium well. It's very common, especially in winter, at northern latitudes, and in people with darker skin.
Common causes
- Little sun exposure or consistent sunscreen use
- Darker skin pigmentation
- Living far from the equator, especially in winter
- Obesity (vitamin D is stored in fat tissue)
- Conditions that reduce fat absorption, such as celiac disease, Crohn's disease or gastric bypass
- Older age (the skin makes less vitamin D)
- Some medications, including certain anti-seizure drugs and glucocorticoids
What can help
- Talk with a clinician about a vitamin D supplement and the right dose
- Eat vitamin D sources such as fatty fish, egg yolks and fortified foods
- Get some safe sun exposure when the UV index allows
If it’s high
High levels almost always come from taking large doses of supplements over time. Too much vitamin D can raise blood calcium, which can cause nausea, weakness, kidney stones and, rarely, serious heart or kidney problems.
Common causes
- High-dose vitamin D supplements
- Prescription vitamin D taken longer than intended
- Errors in compounded or mislabeled supplements
What can help
- Review your supplement doses with a clinician
- Ask whether your calcium should be checked if your level is well above 100 ng/mL
Usual ranges
What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.
For adults: 30–100 ng/mL. Source: Quest Diagnostics, Labcorp. Labs treat above 150 ng/mL as urgent.
- Adults (this one applies)30–100 ng/mL
Sources: Quest Diagnostics, Labcorp
See Vitamin D by age and sex, with the U.S. survey numbers where they exist.
Wellness targets
Narrower ranges some clinicians aim for. Being outside one doesn’t mean something is wrong.
30–50 ng/mL (Adults). Evidence: Limited. 20 ng/mL meets bone-health needs for nearly everyone (NAM), and 30 is the most common lab cutoff. Above 50 brings no proven extra benefit and is linked to potential harm, and the Endocrine Society (2024) found too little evidence to set any target.
NIH Office of Dietary Supplements status categories (based on NAM 2011)
- Deficientbelow 12 ng/mL
- Inadequate for some people12 to under 20 ng/mL
- Adequate20 to under 50 ng/mL
- Potential adverse effects50 to under 150 ng/mL
- Associated with toxicity150 and above ng/mL
Endocrine Society 2011 categories (superseded for healthy adults in 2024)
- Deficiencybelow 20 ng/mL
- Insufficiency20 to under 30 ng/mL
- Sufficiency30 and above ng/mL
If this applies to you
Vitamin D means a little more for some people. Open the one that fits you.
Had weight-loss surgery
Low vitamin D is very common in people with obesity before surgery and stays common afterward. ASMBS suggests checking it in everyone, and BOMSS suggests checks at 3, 6 and 12 months, then at least yearly.
Celiac disease or IBD
BSG suggests measuring vitamin D in Crohn's disease and ulcerative colitis, and ACG lists vitamin D among the other tests that may be part of celiac follow-up.
Endurance athlete
Many athletes run low on vitamin D at some times of the year. How much sun reaches the skin and skin type both play a part.
Tracking for long-term health
The Endocrine Society suggests against routine vitamin D testing in the general population at every adult age. It also says the vitamin D levels that bring specific health benefits have not been set in clinical trials.
Age 65 or older
Vitamin D tests are often ordered, but the Endocrine Society suggests against routine vitamin D testing in the general population, including adults 75 and older. Your clinician may still check it for a specific reason.
Perimenopause or menopause
The Endocrine Society notes that ages 50 to 74 are a time of bone loss linked to menopause and aging. Even so, it suggests against routine vitamin D testing for generally healthy people in this age group. NICE suggests talking about bone health at menopause reviews.
Vegan or vegetarian
Vitamin D status depends on sun exposure and on fortified foods or supplements, the Academy notes. How much the skin makes varies with season, latitude, time of day, skin color, sunscreen and clothing.
On a GLP-1 medicine
Vitamin D is also on the 2025 joint advisory's list of nutrients that can run short when calorie intake drops sharply on these medicines.
How common is your level?
NHANES describes the US civilian, non-institutionalized population, not a 'healthy' reference group. People with disease, on medication, fasting or not (except fasting-subsample markers), smokers and so on are all included. A percentile says where a value sits among Americans of that sex and age, not whether it is normal.
Use the left and right arrow keys to read each age. Shift moves five years.
Reference data derived from CDC/NCHS National Health and Nutrition Examination Survey (NHANES), cycles 2015-2016, 2017-2018, August 2021-August 2023. Analysis by bloodtesttracker.com; not endorsed by CDC, NCHS or HHS.
Explore Vitamin D by age and sex: every percentile as a table, with a download.
What can affect your result
- Season: levels are usually lowest in late winter and early spring
- Skin pigmentation, age and body fat
- Latitude and time spent outdoors
- Assay method: immunoassays and LC-MS/MS can differ by 10–20%
- High-dose biotin supplements can falsely raise results on some competitive immunoassays; stop biotin 2–3 days before the draw unless your clinician says otherwise.
- Some immunoassays under-measure vitamin D2 (ergocalciferol); LC-MS/MS measures D2 and D3 separately.
About 2–3 months to settle at a new level after changing sun exposure or supplements.
When to talk to a clinician
See a clinician if your level is below 12 ng/mL (30 nmol/L), especially with bone pain or muscle weakness, or if it's above 100 ng/mL (250 nmol/L) while you're taking supplements.
Questions you could ask
- Does my vitamin D level matter for any of my other conditions or medications?
- Should we look at my calcium level?
- Is my current supplement dose still right for me?
- Do you recommend a vitamin D supplement for me, and at what dose?
- Should we recheck it after a few months, and is my calcium or PTH worth checking?
Questions people ask
Why does my lab say 30–100 when other sources say 20 is enough?
Many US labs adopted 30 ng/mL from the 2011 Endocrine Society guideline, while the National Academy of Medicine concluded 20 ng/mL is enough for bone health in nearly everyone. Both are used, and experts still disagree.
How do I convert ng/mL to nmol/L?
Multiply ng/mL by 2.496, so 30 ng/mL is about 75 nmol/L. To go the other way, multiply nmol/L by 0.4006.
Show the science and sources
Units
- 1 ng/mL = 1 ng/mL
- 1 ng/mL = 2.496 nmol/L
Open the Vitamin D unit converter
Is a change real?
Vitamin D naturally varies about 12.1% from test to test in the same healthy person. Between two results from the same lab, a change of roughly 37% or more is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: Analytical quality goals for 25-vitamin D based on biological variation (Viljoen A et al.).
For clinicians and researchers
25(OH)D (calcifediol) is the major circulating metabolite, with a half-life of about 2–3 weeks, and reflects cutaneous synthesis plus dietary and supplemental D2 and D3. Its production is minimally regulated, which makes it the accepted status marker. 1,25(OH)2D (calcitriol) is tightly regulated by PTH and is not a status marker. Total 25(OH)D is the sum of 25(OH)D2 and 25(OH)D3, and LC-MS/MS can resolve the C3-epimer. Standardization through the CDC VDSCP and NIST reference materials has reduced, but not eliminated, differences between assays. Thresholds remain contested: NAM (2011) sets the RDA-level target at 20 ng/mL, while the Endocrine Society (2011) proposed 30 ng/mL for at-risk patients. The 2024 Endocrine Society guideline recommends against routine screening in healthy adults under 75 and declines to define any target.
LOINC 62292-8 (primary), 35365-6, 1989-3, 14635-7. Specimen: serum-or-plasma.
Sources
- Vitamin D — Fact Sheet for Health Professionals, NIH Office of Dietary Supplements
- Dietary Reference Intakes for Calcium and Vitamin D, Institute of Medicine (National Academies Press) (2011)
- Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline, Journal of Clinical Endocrinology & Metabolism (2024)
- Evaluation, Treatment, and Prevention of Vitamin D Deficiency: an Endocrine Society Clinical Practice Guideline, Journal of Clinical Endocrinology & Metabolism (2011)
- Vitamin D, 25-Hydroxy, Total, Immunoassay (test code 17306), Quest Diagnostics
- Vitamin D, 25-Hydroxy (test 081950), Labcorp
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.