Vitamin D Calculator

Enter your 25-hydroxyvitamin D (25-OH D) blood test result to check which category it falls into.

Vitamin D Calculator

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Vitamin D (25-OH) (ng/mL)

The classification

Deficient: under 20 ng/mL Insufficient: 20-29 ng/mL Sufficient: 30-100 ng/mL Potentially Excessive: over 100 ng/mL

Example

A reading of 32 ng/mL falls in the Sufficient range (30-100).

Step-by-step guide

Get a 25-hydroxyvitamin D blood test - this is the standard test for vitamin D status, distinct from the less commonly ordered 1,25-dihydroxyvitamin D test.
Enter your result in ng/mL (the standard US unit - if your report shows nmol/L, divide by 2.5 to convert).
Read your category and discuss supplementation dosing with a doctor if you're deficient or insufficient.

Why vitamin D deficiency is so common

Vitamin D is unusual among vitamins because your body can produce it from sun exposure on skin, rather than needing it entirely from food - but that makes levels highly dependent on factors like geographic latitude, skin tone, sunscreen use, time spent indoors, and season. This is why an estimated one billion people worldwide have deficient or insufficient levels, making it one of the most common nutrient shortfalls globally, even in sunny climates when most time is spent indoors or covered.

Common mistakes

Mixing up ng/mL and nmol/L - a result reported as "75 nmol/L" is a sufficient 30 ng/mL, not an alarmingly low number if read as ng/mL directly.

Self-dosing very high supplement amounts without monitoring - vitamin D is fat-soluble and can build up to toxic levels over time with excessive supplementation, unlike water-soluble vitamins that are more easily excreted.

Frequently asked questions

How do I convert nmol/L to ng/mL?

Divide your nmol/L value by 2.5 to get ng/mL (for example, 75 nmol/L / 2.5 = 30 ng/mL). Most of the US uses ng/mL, while much of Europe and Canada use nmol/L.

Can vitamin D levels be too high?

Yes - since vitamin D is fat-soluble, it can accumulate to toxic levels, generally above 100 ng/mL, usually from excessive supplementation rather than sun exposure or diet alone. Symptoms of toxicity relate to resulting high calcium levels.

What causes low vitamin D besides lack of sun?

Darker skin tone (which reduces vitamin D synthesis from sunlight), obesity, certain digestive conditions that impair fat absorption, and some medications can all contribute to lower levels, independent of sun exposure alone.

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