Vitamin D, blood levels

Vitamin D, blood levels

Share This Content
Vitamin D tests used in this video

Your personalised vitamins

Single test, £39.99

Year plan, 2 tests and vitamin D supplies to titrate, £75

BetterYou test


Vitamin D into the body

D3 (cholecalciferol), sun, animals or supplement

D2 (ergocalciferol), plants, supplements


In the skin

Vitamin D, cholecalciferol, synthesised in the skin

In the liver

Converted to its major circulating form, 25-hydroxyvitamin D (25(OH)D)


In the kidneys

Converted into 1,25-dihydroxyvitamin D3, or calcitriol, the principal active hormonal form of vitamin D

Vitamin D in the blood

25 hydroxy vitamin D

25-hydroxyvitamin D (25OHD)


Circulating concentration of 25OHD is the accepted biomarker for vitamin D status

Many experts recommend a level between 20 and 40 ng/mL (50 to 100 nmol/L)

Others recommend a level between 30 and 50 ng/mL (75 to 125 nmol/L)

Some say higher

Serum concentrations, units

Nanograms per milliliter (ng/mL)

(1000 ng = 1 microgram)

Nanomoles per liter (nmol/L)

1 ng/mL is equal to 2.5 nmol/L



International units

400 IU = 10 mcg

1,000 IU = 25 mcg

2,000 IU = 50 mcg

4,000 IU = 100 mcg

How much to take in Winter?

Do not take more than 100 micrograms (4,000 IU) of vitamin D a day (11 years to adults)

Children aged 1 to 10 years should not have more than 50 micrograms (2,000 IU) a day.

Infants under 12 months should not have more than 25 micrograms (1,000 IU) a day.

Prostate cancer

Colon cancer

Breast cancer

Multiple sclerosis

Heart disease




Chronic pain and sleep


Cytokine storm