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Signs of low vitamin D, who is at risk, how it is tested and treated, and the real benefits of vitamin D for bones and health.
By Editorial Team · Updated · 2 min read
This article is awaiting review by a qualified medical professional.
Quick answer
Vitamin D deficiency often causes no symptoms, but it can lead to tiredness, bone pain and muscle weakness, and in severe cases to soft bones (rickets in children, osteomalacia in adults). It is caused by little sun exposure, dark skin, older age, obesity and some digestive diseases. It is diagnosed with a blood test and treated with supplements, sensible sun exposure and diet.
Vitamin D helps your body absorb calcium and keeps bones, teeth and muscles healthy. Your skin makes it when exposed to sunlight, and you also get small amounts from food. Deficiency is common worldwide, including in sunny countries.
The main proven benefit is treating or preventing deficiency. In people who already have normal levels, extra vitamin D has not been shown to reduce fractures, cancer or heart disease.
Many people have no symptoms. When present they can include:
A blood test measures 25-hydroxyvitamin D. Doctors usually test people with symptoms or higher risk rather than everyone.
See a doctor if you have bone pain, muscle weakness or frequent falls, or if you are at higher risk and want to be tested. Babies and pregnant or breastfeeding women should ask a healthcare provider about the right supplement dose.
It depends on the guideline. Many labs and the US National Institutes of Health treat below 12 ng/mL (30 nmol/L) as deficient and 12 to 20 ng/mL (30 to 50 nmol/L) as inadequate for some people, while the Endocrine Society uses below 20 ng/mL. Your doctor will interpret your result.
The recommended intake for most adults is 600 IU (15 micrograms) a day, and 800 IU (20 micrograms) for people over 70. The upper safe limit for adults is 4,000 IU (100 micrograms) a day unless a doctor advises a higher treatment dose.
Yes. Very high doses over time can raise blood calcium and cause nausea, vomiting, weakness and kidney problems. Avoid high-dose supplements unless a doctor has recommended them.
Large trials have not shown that extra vitamin D prevents fractures, cancer or heart disease in people with normal levels. The clearest benefit is correcting a deficiency.
This article is for educational purposes only and does not replace advice from a doctor or other qualified health professional. See our medical disclaimer.
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