Low blood magnesium

Clinically: Hypomagnesaemia · also low magnesium, magnesium deficiency, low blood magnesium

electrolyte MONDO MONDO:0006844 unverified

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 Magnesium, interpreted alongside symptoms and history rather than read off a report. Note that a normal-looking result does not reliably rule this out -- see the caveats above.

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

Magnesium in the blood is below normal. It can come from poor diet, losses from the gut such as long-lasting diarrhoea, or losses through the kidneys.

Serum magnesium concentration below 0.66 mmol/L (1.6 mg/dL), with or without total body magnesium depletion; clinically significant signs and symptoms usually do not appear until serum magnesium falls below 0.5 mmol/L (1.2 mg/dL). Causes include low intake, gastrointestinal losses and renal losses.

caveats unverified

Blood holds less than 1% of the body's magnesium. So the blood level can be normal even when the body's stores are low. Low magnesium often comes with low potassium and low calcium.

No clinical version written yet.

The typical lab pattern

What the diagnosis rests on

The results a diagnosis is actually made on.

Magnesium

low

—

Typically defined as serum magnesium below 0.66 mmol/L (1.6 mg/dL). Serum holds under 1% of body magnesium, so a normal result does not rule out low body stores.

Consistent with it

Fits the picture, but not enough on its own.

Potassium	low	—	Low potassium is common with low magnesium, and does not correct until magnesium is replaced.
Calcium, total	low	—	Low calcium is common with low magnesium. It does not respond to calcium or vitamin D alone; magnesium treatment corrects it.

How it usually feels

Feeling sick to your stomach · occasional
Feeling tired all the time · occasional
Headaches · occasional
Loss of appetite · occasional
Muscle cramps or spasms · occasional
Muscles feeling weak · occasional
Noticing your heartbeat · occasional
Pins and needles, or numbness · occasional

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.