Vitamin D Level Calculator

Enter your 25-hydroxyvitamin D (25(OH)D) result and see whether it's deficient, insufficient, or sufficient — computed instantly in your browser, nothing sent anywhere.

Vitamin D is measured, not calculated, from a 25(OH)D blood test. The Endocrine Society defines under 10 ng/mL as severely deficient, 10–29 ng/mL as deficient, and 30 ng/mL or above as sufficient. Many labs print a wider "normal" range on the report, but a result inside that range can still sit in the deficient zone by this guideline.

Endocrine Society thresholds ng/mL and nmol/L Medically reviewed
Units
Enter your vitamin D result to see where it falls. Everything is computed locally in your browser — no data leaves this page.

What your result means

These are the Endocrine Society Vitamin D Clinical Practice Guideline thresholds. There is no coded upper "toxicity" cutoff here deliberately — your lab's own high flag or your clinician should confirm toxicity risk at unusually high levels.

Category25(OH)D (ng/mL)25(OH)D (nmol/L)
Severely deficientBelow 10Below 25
Deficient10–29.925–74.9
Sufficient30 or above75 or above
"Normal" isn't the same as optimal
Some labs print a reference range starting as low as 20 ng/mL, so a result of 24 or 26 ng/mL can come back with no flag at all. By the Endocrine Society's guideline that same value is still in the deficient range (10–29.9 ng/mL) and worth acting on — a lab printing "in range" doesn't mean nothing needs fixing.

My vitamin D is 24 nmol/L — how much should I take?

A direct walk-through of the conversion and what the guideline says at this level.

nmol/L to ng/mL conversion
ng/mL = nmol/L ÷ 2.496
24 nmol/L ÷ 2.496 ≈ 9.6 ng/mL

9.6 ng/mL falls under the Endocrine Society's severely deficient threshold of 10 ng/mL. At this level, prescription-dose repletion is usually the appropriate next step rather than a standard over-the-counter dose — this is a see-your-doctor-within-a-week situation, not one to self-treat.

Once repletion is underway and levels start rising, an ongoing maintenance dose is commonly in the range of 2,000–4,000 IU of vitamin D3 daily, taken with a fat-containing meal to help absorption. Levels typically rise meaningfully within 8–12 weeks of consistent dosing, which is when a retest makes sense; mood, energy, and sleep quality can start to improve within 4–8 weeks.

Frequently asked questions

How do I calculate my vitamin D levels?
You don't calculate vitamin D from other values — it's measured directly with a 25-hydroxyvitamin D (25(OH)D) blood test, reported in ng/mL in the US or nmol/L in the UK and much of Europe. Enter your result and unit into the calculator above; it converts nmol/L to ng/mL and classifies the result as deficient, insufficient, or sufficient using the Endocrine Society's guideline thresholds.
My vitamin D level is 24 nmol/L. How much vitamin D should I take?
24 nmol/L converts to about 9.6 ng/mL (divide nmol/L by 2.496), which falls under the Endocrine Society's severely deficient threshold of 10 ng/mL. At this level, prescription-dose repletion is usually appropriate rather than a standard over-the-counter dose — see a doctor within the next week rather than self-treating. Once repletion is underway, an ongoing maintenance dose is commonly in the range of 2,000–4,000 IU of vitamin D3 daily, taken with a fat-containing meal, with a retest around 8–12 weeks.
What drains vitamin D from your body?
Limited sun exposure, higher body fat (vitamin D is fat-soluble and gets sequestered in fat tissue), darker skin pigmentation, aging skin, malabsorption conditions such as celiac or Crohn's disease, and medications including anticonvulsants and glucocorticoids all reduce how much active vitamin D circulates in your blood. Liver or kidney disease can also impair the two conversion steps that turn vitamin D into its active form.
Note: This calculator is for informational purposes and does not replace medical advice. It does not assess toxicity risk at very high levels — interpret an unusually high result together with your lab's own flag and your clinician.

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