Lab test glossary · Other
Magnesium: what it means
Also known as: Mg, serum magnesium
Magnesium is an electrolyte your muscles, nerves, and heart depend on; low levels are common and can cause cramps and affect heart rhythm.
What it measures
Magnesium is an electrolyte involved in hundreds of processes, from muscle and nerve function to blood-sugar and blood-pressure regulation. The blood test captures only a small fraction of the body's total (most is in bone and cells), so a normal level doesn't fully rule out depletion — but a low level is worth acting on.
Typical range
Often roughly 1.7–2.2 mg/dL.
Reference ranges differ between labs and are printed on your own report — always read your result against that range, not a general one.
What a high result can mean
- Reduced kidney function
- Excess magnesium-containing supplements or antacids
A high value is a starting point for a conversation, not a diagnosis — many causes are benign or temporary.
What a low result can mean
- Gastrointestinal losses (diarrhea, vomiting)
- Diuretics, alcohol, or poorly controlled diabetes
- Poor intake or absorption
Why the trend matters
Because the blood test underestimates total-body magnesium, the trend and your symptoms matter alongside any single value.
When to talk to your doctor
A low magnesium — especially with cramps, palpitations, or on diuretics — is worth reviewing with your doctor.
This page is general education about a common lab test — it isn’t medical advice and can’t interpret your specific result. What a value means depends on your history, symptoms, and the rest of your labs, which is a conversation for you and your clinician.