Quick answer: for vitamin D levels (25-hydroxy vitamin D), under 12 ng/mL (30 nmol/L) puts you at risk of deficiency, 12 to 20 ng/mL (30 to 50 nmol/L) may be inadequate for some people, 20 ng/mL (50 nmol/L) or more is sufficient for most, and above 50 ng/mL (125 nmol/L) can be linked to harm (National Academies, via the NIH Office of Dietary Supplements). The Endocrine Society's 2011 guideline used a higher bar, calling under 20 ng/mL deficient and 21 to 29 ng/mL insufficient.
Vitamin D levels: normal range
| 25(OH)D ng/mL | nmol/L | Meaning | Source |
|---|---|---|---|
| Under 12 | Under 30 | At risk of deficiency | National Academies (NIH ODS) |
| 12 to 20 | 30 to 50 | Potentially inadequate for some people | National Academies (NIH ODS) |
| 20 or more | 50 or more | Sufficient for most people | National Academies (NIH ODS) |
| Above 50 | Above 125 | Can be associated with adverse effects | National Academies (NIH ODS) |
| Under 20 / 21 to 29 | Under 50 / 52.5 to 72.5 | Deficiency / insufficiency | Endocrine Society, 2011 |
To convert, multiply ng/mL by 2.5 to get nmol/L (or divide nmol/L by 2.5). US labs usually report ng/mL; most other countries use nmol/L. MedlinePlus notes that many experts recommend 30 to 80 ng/mL (75 to 200 nmol/L), so your lab may flag a result under 30 even though it meets the 20 ng/mL standard.
Why 20 and 30 ng/mL both get quoted
The National Academies (then the Institute of Medicine) set 20 ng/mL in 2011 as the level that is sufficient for bone health in most people. The Endocrine Society's 2011 guideline, aimed at people at risk, called anything under 30 ng/mL less than ideal. In 2024 the Endocrine Society published a new guideline that did not set a target: it found no clear evidence defining the optimal level for disease prevention and suggested against routine vitamin D testing in healthy people. It suggests supplementation for children and teens, adults over 75, pregnancy and high-risk prediabetes, and against going above standard intakes for healthy adults under 75.
National Academies thresholds via the NIH Office of Dietary Supplements; MedlinePlus. Multiply by 2.5 for nmol/L.
So a 24 ng/mL result is fine by the National Academies standard but below the 30 ng/mL that the 2011 Endocrine Society guideline and many experts prefer. Neither camp treats it as an emergency.
Worked example: 17 ng/mL in late winter
Say a 35-year-old office worker who takes no supplements tests in March and gets 17 ng/mL (42.5 nmol/L). By the National Academies standard that is in the 12 to 20 ng/mL band, potentially inadequate for some people, and 3 ng/mL short of the level sufficient for most. By the 2011 Endocrine Society definitions it is deficient (under 20). It is still well above the 12 ng/mL deficiency-risk line.
What might explain it: little sun exposure and not enough vitamin D in the diet are the first causes MedlinePlus lists, and skin production drops with season and latitude. MedlinePlus also lists bowel conditions that reduce fat absorption, liver or kidney disease and medicines such as phenytoin.
Questions to take to the doctor:
- Do I need a supplement, and at what dose, given the 600 IU daily standard intake for adults 19 to 70?
- Is there any reason to suspect an absorption problem?
- When should I retest? Levels shift over weeks, so allow about two months after a change.
What is vitamin D?
Vitamin D helps your gut absorb calcium and keeps bones strong. Your skin makes it from sunlight, and it comes from a few foods and supplements. The blood test measures 25-hydroxy vitamin D, or 25(OH)D, the storage form that reflects intake and sun exposure over recent weeks.
What low vitamin D means
Long-term deficiency can weaken bones. MedlinePlus lists these causes of low levels:
- Little sun exposure, and not enough vitamin D in the diet
- Conditions that reduce fat absorption, such as some bowel diseases
- Liver or kidney disease
- Some medicines, including phenytoin, phenobarbital and rifampin
What high vitamin D means
High levels almost always come from taking too much in supplements, not from the sun. MedlinePlus warns that excess vitamin D can raise blood calcium and damage the kidneys. The National Academies flag levels above 50 ng/mL (125 nmol/L) as a possible concern. If yours is high, review your supplements with your doctor.
What moves vitamin D
- Intake: the Endocrine Society's 2024 guideline cites the standard intake of 600 IU a day for adults 19 to 70.
- Sun: skin production varies with season, latitude, skin tone and sunscreen.
- Supplements: useful when intake is low, but more is not better. Ask your doctor before taking high doses, especially if you have kidney disease or take other medicines.
Levels shift over weeks, not days, so allow a couple of months after changing your intake before you retest.
How to test vitamin D
Ask for 25-hydroxy vitamin D; the 1,25-dihydroxy form is a different test used for specific conditions. MedlinePlus says you usually do not need to fast, though it depends on the lab. Results vary somewhat between labs and methods, so use the same lab for repeat tests when you can. Given the 2024 guideline, routine testing is most useful if you have a reason: a condition affecting absorption, bone loss, or a supplement dose you want to check.
Which at-home tests include vitamin D
Vitamin D (25-OH) is on three SiPhox panels: Longevity Essentials, Ultimate 360 and GLP Optimization. Heart & Metabolic, Thyroid Focus and Hormone Focus do not include it.
| SiPhox panel | Biomarkers per test | Per test, with shipping | Listed as |
|---|---|---|---|
| Longevity Essentials | 31 | $149 | Vitamin D (25-OH) (Nutrition) |
| Ultimate 360 | 62 | $274 | Vitamin D (25-OH) (Nutrition) |
| GLP Optimization | 46 | $224 | Vitamin D (25-OH) (Nutrition) |
Longevity Essentials pairs it with ferritin; Ultimate 360 and GLP Optimization add B12, folate and iron. Collection is from the upper arm at home, and SiPhox does not include a doctor review. See our SiPhox review and the longevity blood test comparison.
Longevity Essentials
The default panel: heart, metabolic, hormone and inflammation markers in one draw.
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GLP Optimization
Built for people on GLP-1 medication: metabolic, liver, kidney, nutrient and iron markers.
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Ultimate 360
Everything on the four core panels plus iron studies, B12 and folate, GGT and PSA.
Check price
Frequently asked questions
What is a normal vitamin D level?
20 ng/mL (50 nmol/L) or more is sufficient for most people by the National Academies standard. MedlinePlus notes many experts recommend 30 to 80 ng/mL, in line with the Endocrine Society's 2011 guideline.
Is 25 ng/mL of vitamin D low?
Not by the National Academies standard, which calls 20 ng/mL or more sufficient for most. It is below the 30 ng/mL that the 2011 Endocrine Society guideline used, so some labs flag it.
What vitamin D level is too high?
The National Academies say levels above 50 ng/mL (125 nmol/L) can be associated with adverse effects. High levels usually come from supplements.
How do I convert vitamin D from ng/mL to nmol/L?
Multiply ng/mL by 2.5. For example, 20 ng/mL is 50 nmol/L and 30 ng/mL is 75 nmol/L.
Should everyone get a vitamin D test?
The Endocrine Society's 2024 guideline suggests against routine testing in healthy people, because no target level has been proven to prevent disease. Testing makes sense if you have a specific reason.
Sources
- NIH Office of Dietary Supplements: Vitamin D fact sheet for health professionals
- Ross AC et al. The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine. J Clin Endocrinol Metab 2011
- Holick MF et al. Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 2011
- Demay MB et al. Vitamin D for the prevention of disease: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 2024
- MedlinePlus: 25-hydroxy vitamin D test
- SiPhox Health: panel comparison and biomarker lists (checked 29 Sep 2026)