Side effects of low vitamin D

Vitamin D helps the body handle calcium and supports normal bone and muscle function. Low levels may be associated with tiredness, muscle weakness, aches or joint discomfort. Some people also notice low mood or more frequent infections, although these symptoms have many possible explanations. Prolonged deficiency can weaken bones and make injury more concerning; a stress fracture may cause focused pain that worsens with activity. Read about [Vitamin D Deficiency](/conditions/vitamin-d-deficiency/), [Generalised Weakness](/symptoms/generalised-weakness/) and [Joint Pain](/symptoms/joint-pain/).

Ask a clinician whether a blood test is appropriate if symptoms persist or you have risk factors such as limited sun exposure, absorption problems, or a diet low in vitamin D sources. Do not take high-dose supplements without advice; excessive vitamin D can also cause harm. A clinician can recommend a suitable product and explain food, sunlight and follow-up choices for you. Mention medicines and kidney or parathyroid problems before taking supplements. Addressing [Fatigue](/symptoms/fatigue/) or [Low Mood](/symptoms/low-mood/) also means checking for other causes rather than assuming vitamin D is responsible.

Seek prompt assessment for sudden severe bone pain, pain after a minor injury, inability to bear weight, or weakness that is rapidly worsening. These may indicate a fracture or another medical problem. Arrange review for persistent low mood, frequent infections or marked fatigue. Seek emergency help for confusion, collapse, severe vomiting or breathing difficulty, especially after taking supplements, as these symptoms can have urgent causes.

Ask whether vitamin D testing is needed, what may have caused a low result, which supplement and dose are suitable, and when to repeat assessment. Ask how to protect bone health and whether weakness or pain needs another explanation.