Vitamin D Levels Explained: Deficiency, Normal and High

Vitamin D is measured as 25-hydroxy vitamin D (25-OH D). Below 20 ng/mL (50 nmol/L) is usually called deficient, 20–29 ng/mL is insufficient, and 30–100 ng/mL is sufficient. Above 100 ng/mL is too high. Low vitamin D is very common, especially in people who get little sun, have darker skin or cover most of their skin.

Check your result with the free Vitamin D Test Checker. It accepts ng/mL or nmol/L and explains what your level means. Your result never leaves your device.

What do vitamin D test results mean?

Level (ng/mL)	Level (nmol/L)	Band
Below 20	Below 50	Deficient
20 to 29	50 to 74	Insufficient
30 to 100	75 to 250	Sufficient
Above 100	Above 250	Too high

To convert ng/mL to nmol/L, multiply by 2.5. These bands follow the Endocrine Society's widely used cut-offs. Some bodies, including the US Institute of Medicine, consider 20 ng/mL enough for bone health in most people, so the "insufficient" zone is debated. Your doctor will choose a target for you.

Why is vitamin D important?

Vitamin D helps your body absorb calcium and phosphorus, which keep bones and teeth strong. It also supports muscle function. Very low levels over a long time can cause bone pain, muscle weakness and softened bones (osteomalacia in adults, rickets in children), and raise the risk of falls and fractures in older people.

Why is vitamin D often low?

Most vitamin D is made in the skin from sunlight. Levels tend to be low with:

• Little time outdoors, office work, or covering most of the skin
• Darker skin, which needs more sun to make the same amount
• Winter months and northern latitudes
• Older age, obesity, pregnancy and breastfeeding
• Conditions that affect absorption (such as coeliac disease) and some medicines

Food provides only small amounts: oily fish, egg yolks, fortified milk, yogurt and cereals.

How do I check my vitamin D result?

1. Open the Vitamin D Test Checker.
2. Choose Enter values and type your 25-OH vitamin D with its unit (ng/mL or nmol/L). You can also paste the whole report or upload a digital lab PDF; the checker recognises names like "25-OH Vitamin D" and "Vitamin D Total".
3. Read your band, what it means and the questions to ask your doctor.

If your report also includes calcium, vitamin B12 or ferritin, add them too: the checker explains those as well.

How can I raise low vitamin D safely?

• Sunlight: short, regular sun on arms and face, without burning, helps many people. The amount needed depends on skin tone, season and location.
• Food: add oily fish, eggs and fortified foods.
• Supplements: the usual choice for deficiency. Your doctor will pick a dose based on your level, weight and health. Vitamin D3 is commonly used.

Don't take very high doses on your own. Too much vitamin D raises blood calcium, which can cause nausea, thirst, frequent urination, confusion and kidney stones. Levels above 100 ng/mL are flagged as too high, and very high levels (around 150 ng/mL) as needing urgent advice.

When should I see a doctor?

See your doctor if your level is deficient, if you have bone pain, weakness or frequent falls, or if you have kidney disease, since vitamin D handling is different then. If you take high-dose supplements and feel very thirsty, sick or confused, get your calcium checked promptly.

For a balanced eating pattern that includes vitamin D foods, see the healthy diet plan guide, and read how to read a blood test report. When you're ready, check your vitamin D level.