What severe vitamin D deficiency can result in

Vitamin D helps the body absorb calcium and supports normal bone and muscle function. A severe deficiency may cause diffuse bone discomfort, muscle aches, cramps, or generalised weakness that makes stairs or rising from a chair harder. Some people have few symptoms, while others notice fatigue, low mood, or frequent infections; these symptoms have many possible causes and do not confirm a deficiency. Prolonged deficiency can impair bone mineralisation and make bones more vulnerable to injury, including a stress fracture.

Book a medical review if symptoms persist or a blood test has shown a very low vitamin D level. A clinician may review diet, sun exposure, medicines, digestive conditions, kidney or liver problems, and factors such as obesity that can affect vitamin D status. Treatment may involve a prescribed replacement plan, followed by maintenance advice and repeat testing when appropriate. Do not take large doses without guidance: excess vitamin D can raise calcium and harm the kidneys. Support bone health with suitable movement and adequate dietary calcium unless a clinician advises otherwise.

Seek prompt assessment for sudden severe bone pain, pain after a minor injury, inability to bear weight, or worsening weakness, because these may indicate a fracture or another condition. Get urgent help for confusion, repeated vomiting, severe thirst with frequent urination, or marked dehydration while taking supplements; these can signal a calcium problem. Arrange routine follow-up for persistent fatigue, low mood, or recurrent infections rather than assuming vitamin D is the only explanation.

Ask which test results define the problem, what dose and duration are suitable, whether calcium or other tests are needed, and when your symptoms and blood level should be reviewed.