Low blood calcium

Clinically: Hypocalcaemia · also low calcium, low blood calcium, calcium deficiency

electrolyte

This describes what this condition typically looks like. It is not a diagnosis and cannot tell you whether you have it -- patterns overlap, results vary between labs, and the same numbers mean different things in different people. Diagnosis usually rests on Calcium, total, interpreted alongside symptoms and history rather than read off a report.

unverified These explanations are written to be easy to read and have not yet been checked against a source. The ranges and measurement notes on this page show theirs.

definition unverified

Calcium in the blood is below normal. Common causes are an underactive parathyroid gland, often after neck surgery, and too little vitamin D or magnesium.

Serum calcium (adjusted for albumin) below the reference range. In the Society for Endocrinology emergency guidance, severe hypocalcaemia is serum calcium below 1.9 mmol/L and/or symptoms at any level below the reference range, and mild hypocalcaemia is asymptomatic with serum calcium above 1.9 mmol/L. The most common cause of acute symptomatic hypocalcaemia in hospital is loss of parathyroid function after total thyroidectomy.

caveats unverified

Total calcium has to be read next to albumin. Low blood protein makes calcium read low. Many people with low calcium have no symptoms.

No clinical version written yet.

The typical lab pattern

What the diagnosis rests on

The results a diagnosis is actually made on.

Calcium, total

low

—

Serum calcium, adjusted for albumin, below the reference range. Severity grading (Society for Endocrinology emergency guidance): severe is below 1.9 mmol/L or any low level with symptoms; mild is above 1.9 mmol/L without symptoms.

Consistent with it

Fits the picture, but not enough on its own.

Albumin	low	—	Calcium is adjusted for albumin. Low blood protein makes total calcium read low.
Magnesium	low	—	Part of the first work-up. Low magnesium is a cause, for example with acid-reducing PPI medicines, and must be treated as well.
25-hydroxyvitamin D	low	ref 20–50	Part of the first work-up. Severe vitamin D deficiency is one of the causes.
Phosphate	either	—	Part of the first work-up, alongside calcium and parathyroid hormone. The guidance does not give a direction.

How it usually feels

Frequencies say how often a symptom accompanies this condition — not the other way round. Most people with any of these symptoms do not have this.