High calcium and low vitamin D: what to know

Calcium in blood is controlled by the bones, kidneys, intestines and hormones. Vitamin D helps the intestine absorb calcium, so a low vitamin D result does not automatically explain a high calcium result. The meaning depends on whether the test measured total or adjusted calcium, the degree of change, symptoms, medicines and kidney function. A repeat test and related checks may be needed before a cause is considered. Results should be interpreted together rather than in isolation.

Contact the clinician who requested the tests and bring a list of supplements, antacids and prescription medicines. Do not increase vitamin D or calcium on your own while calcium is high. Keep normally hydrated unless you have been given a fluid restriction, and follow the planned repeat testing. Tell the clinician about bone pain, fatigue, weakness, constipation, thirst or changes in urination. A review may include kidney tests, hormone-related tests and an assessment of bone health.

Seek prompt medical advice if high calcium is accompanied by persistent vomiting, marked thirst, confusion, unusual drowsiness, severe weakness or very little urine. Emergency help is appropriate for collapse, a seizure, severe confusion or difficulty staying awake. Low vitamin D alone often causes no clear symptoms, so urgency is guided by the high calcium level and how you feel.

Was my calcium adjusted for albumin, and should it be repeated? Could a medicine or supplement be affecting it? How should vitamin D be managed safely while calcium is elevated?