What should you know about the impact of low vitamin D?

Vitamin D helps the body absorb calcium and supports normal bone and muscle function. When levels are low, some people notice tiredness, generalised weakness, muscle aches or joint pain; others have no clear symptoms. Longer-lasting deficiency can reduce bone strength and make an injury such as a stress fracture more likely. Low mood or repeated infections can occur alongside deficiency, but these symptoms have many possible explanations. A blood test and your health history help a clinician decide whether vitamin D deficiency is present and whether another cause needs attention.

Arrange a medical review if symptoms persist or a test has shown a low level. Your clinician may recommend a vitamin D supplement, with the dose and duration matched to your result, diet and health conditions. Do not take large doses without advice, because excess vitamin D can disturb calcium balance. Include vitamin-D-containing foods where suitable, and discuss safe sunlight exposure for your skin type and circumstances. Follow-up testing may be suggested when treatment has been underway.

Seek prompt medical advice for new severe bone pain, a suspected fracture, marked muscle weakness or difficulty walking. Contact a clinician if fatigue, low mood or frequent infections are persistent, worsening or affecting daily activities; these concerns should not automatically be attributed to vitamin D. Seek urgent help for sudden inability to use a limb, severe pain after a minor injury, confusion or repeated vomiting.

Ask which test result supports the diagnosis, whether your symptoms could have another cause, which supplement and dose are appropriate, when improvement should be reviewed, and whether your medicines or medical conditions affect vitamin D treatment.