Severe vitamin D deficiency: what to know

Vitamin D helps the body handle calcium and maintain bone and muscle function. Marked deficiency may cause diffuse bone or [Joint Pain](/symptoms/joint-pain/), cramps, muscle aches, difficulty climbing stairs or rising from a chair, and [Generalised Weakness](/symptoms/generalised-weakness/). Some people also report [Fatigue](/symptoms/fatigue/) or [Low Mood](/symptoms/low-mood/), although these symptoms have many possible causes. Weak bones can be more vulnerable to injury, including a [Stress Fracture](/conditions/stress-fracture/). Symptoms alone cannot show how low the level is; a clinician may use a blood test and review diet, medicines, sun exposure and medical conditions such as [Obesity](/conditions/obesity/).

Arrange a clinical review if pain, weakness or fatigue persists, especially if movement is becoming harder. Do not take high-dose supplements without advice: the right preparation and duration depend on your blood results, kidney health, calcium level and other medicines. A clinician may recommend a replacement plan, dietary changes and a follow-up test. Gentle activity within your ability can help preserve function, while severe weakness or pain should be assessed before you increase exercise. Keep a list of supplements and medicines so the dose can be checked safely.

Seek urgent help for sudden inability to walk, severe new bone pain after a minor injury, muscle spasms with confusion, repeated vomiting, severe thirst with frequent urination, or weakness that affects breathing or swallowing. These features may indicate a fracture, an abnormal calcium level or another problem that needs prompt assessment. Frequent infections should also be discussed with a clinician rather than attributed automatically to vitamin D deficiency; see [Frequent Infections](/symptoms/frequent-infections/).

Ask whether your symptoms fit deficiency, which blood tests are needed, what replacement dose is suitable, whether calcium should be checked, when progress will be reviewed, and how to protect your bones while strength returns.