A Normal Vitamin D Level

A Normal Vitamin D Level

For most people, an adequate blood level of vitamin D (measured as 25-hydroxyvitamin D, or 25(OH)D) is considered to be 50 nmol/L (20 ng/mL) or higher.

Vitamin D blood levels are typically reported in either nanomoles per litre (nmol/L) or nanograms per millilitre (ng/mL). The approximate conversion is:

1 ng/mL = 2.5 nmol/L (or 1 nmol/L = 0.4 ng/mL)

Reference Ranges

Reference ranges generally fall into the following categories:

• Deficient: Below 25 nmol/L (<10 ng/mL)
• Insufficient: 25–50 nmol/L (10–20 ng/mL)
• Sufficient (Adequate): 50–75 nmol/L (20–30 ng/mL)
• Above 75 nmol/L: Generally considered adequate for bone health, although higher levels are not routinely recommended for most healthy adults.

What the Ranges Mean

Sufficient (50 nmol/L and above)
This level is considered adequate to maintain bone health and support normal muscle function for most people.

Insufficient (25–50 nmol/L)
This level may not cause immediate symptoms but may be inadequate to maintain long-term bone health. Your GP may recommend increasing your dietary vitamin D intake or taking a supplement.

Deficient (Below 25 nmol/L)
This level is considered too low and can lead to weakened bones, causing rickets in children and osteomalacia in adults. Treatment with higher-dose vitamin D supplements may be recommended under medical supervision.

NHS Guidance

If you live in the UK, the NHS vitamin D guidance recommends that adults and children over the age of 1 consider taking a daily supplement containing 10 micrograms (400 IU) of vitamin D during the autumn and winter months.

People at increased risk of vitamin D deficiency—including those with limited sun exposure, darker skin, people who cover most of their skin outdoors, or those who are housebound—may be advised to take a vitamin D supplement throughout the year.

Readers in the United States can refer to the National Institutes of Health (NIH) Office of Dietary Supplements – Vitamin D Fact Sheet for comprehensive, evidence-based information on recommended intakes, blood levels, dietary sources, and supplementation.

For personalised advice, consult your GP or local healthcare provider.