Low vitamin D: what to know

Vitamin D helps the body absorb calcium and supports bones and muscles. Low levels may be linked with fatigue, generalised weakness, muscle aches, joint pain, low mood, or frequent infections, although these symptoms have many other causes. Limited sun exposure, darker skin, covering most of the skin, malabsorption, some medicines, and obesity can increase the chance of low levels. A blood test is the usual way to assess vitamin D, alongside your symptoms and medical history.

Long-standing deficiency can weaken bones and contribute to bone pain or a stress fracture. The result should be interpreted with calcium, kidney health, diet, and other relevant findings rather than treated in isolation.

Ask a clinician whether testing is appropriate before starting a high-dose supplement. If deficiency is confirmed, use the recommended product and schedule; more is not necessarily better, and excessive supplementation can cause harm. Discuss safe sunlight habits, dietary sources, and whether an underlying absorption problem or medicine needs review. Keep a record of the supplement name and dose, and mention it before adding calcium or another vitamin product.

Arrange an appointment for unexplained persistent fatigue, weakness, bone or joint pain, repeated falls, or a suspected stress fracture. Seek prompt care for severe bone pain, inability to bear weight, new confusion, vomiting, marked thirst, or passing urine unusually often after taking supplements. These symptoms can have causes other than vitamin D deficiency and need assessment rather than self-treatment.

Should I have a vitamin D blood test? Could another condition explain my symptoms? Which supplement and schedule are suitable for me? Do my medicines, diet, or digestion affect vitamin D? When should levels or symptoms be reviewed?