Magnesium blood test
In short
A typical adult magnesium result is 1.6 to 2.6 mg/dL. A high magnesium is uncommon when the kidneys work well. It most often comes from kidney disease or from magnesium in laxatives, antacids or supplements. Always read your result against the range printed on your own report.
A mineral that keeps muscles, nerves and the heartbeat steady.
Magnesium works closely with potassium and calcium, and the kidneys keep its level steady. Only about 1% of the body's magnesium is in the blood, so a mild shortage can be missed. Doctors check it for cramps, an uneven heartbeat, kidney disease, or when potassium or calcium is low.
Is my Magnesium high or low?
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Typical range
| For | Range | Unit |
|---|---|---|
| Adults | 1.6–2.6 | mg/dL |
| Adults | 0.66–1.07 | mmol/L |
Typical ranges for adults. Labs differ a little, so the range printed next to your result is the one to go by.
If your Magnesium is high
A high magnesium is uncommon when the kidneys work well. It most often comes from kidney disease or from magnesium in laxatives, antacids or supplements.
Common reasons
- Red cells breaking open in the tube after the draw (hemolysis)
- Magnesium supplements, or laxatives and antacids that contain magnesium
- Kidney disease, which makes it harder to clear magnesium
- Being low on fluids (dehydration)
- Some mood-stabilizing medicines
- Less often: underactive adrenal or thyroid glands
If your Magnesium is low
A low magnesium is fairly common and often goes with low potassium or low calcium. Common reasons are diarrhea, alcohol, some medicines and poorly controlled diabetes.
Common reasons
- Long-term use of acid-lowering medicines for heartburn
- Some water pills (diuretics) and some chemotherapy medicines
- Diarrhea that lasts, or gut problems that limit absorption
- Heavy alcohol use
- Poorly controlled diabetes, which washes magnesium out in the urine
- Eating very little for a while
- Less often: an inflamed pancreas (pancreatitis)
What can throw it off
Red cells breaking open in the tube (hemolysis) can make magnesium read falsely high.
When it can’t wait
A Magnesium of 4.8 mg/dL or more, or 1 mg/dL or less, usually needs a doctor's attention the same day. Call your doctor’s office, or their after-hours line. If you feel very unwell, call your local emergency number.
Questions to take to your appointment
- 1Could my medicines or supplements explain this?
- 2Should my potassium and calcium be checked too?
- 3Do my kidney results play a part?
Read together with
Doctors rarely read Magnesium alone. These usually sit next to it.
Quick answers
What is the magnesium blood test?
Magnesium: A mineral that keeps muscles, nerves and the heartbeat steady. Magnesium works closely with potassium and calcium, and the kidneys keep its level steady. Only about 1% of the body's magnesium is in the blood, so a mild shortage can be missed. Doctors check it for cramps, an uneven heartbeat, kidney disease, or when potassium or calcium is low.
What is a normal magnesium level?
For most adults, magnesium is typically 1.6 to 2.6 mg/dL. Some countries print it in mmol/L, so check the unit first. Labs differ a little, so the range printed next to your result is the one to go by.
What does a high magnesium mean?
A high magnesium is uncommon when the kidneys work well. It most often comes from kidney disease or from magnesium in laxatives, antacids or supplements. Common reasons include red cells breaking open in the tube after the draw (hemolysis); magnesium supplements, or laxatives and antacids that contain magnesium; kidney disease, which makes it harder to clear magnesium; and being low on fluids (dehydration). A doctor reads it together with your other results and how you feel.
What does a low magnesium mean?
A low magnesium is fairly common and often goes with low potassium or low calcium. Common reasons are diarrhea, alcohol, some medicines and poorly controlled diabetes. Common reasons include long-term use of acid-lowering medicines for heartburn; some water pills (diuretics) and some chemotherapy medicines; diarrhea that lasts, or gut problems that limit absorption; and heavy alcohol use.
What can affect my magnesium result?
Red cells breaking open in the tube (hemolysis) can make magnesium read falsely high.
When is my magnesium result urgent?
A magnesium result of 4.8 mg/dL or more, or 1 mg/dL or less usually needs a doctor's attention the same day. Call your doctor's office or their after-hours line. If you feel very unwell, call your local emergency number.
What should I ask my doctor about my magnesium?
Questions worth taking to the appointment: Could my medicines or supplements explain this? Should my potassium and calcium be checked too? Do my kidney results play a part?
What this page can’t do
It reads each number on its own.
Doctors read results together — ALT with AST, ferritin with hemoglobin, TSH with free T4. A pattern says more than any single flag.
It doesn't know you.
Your age, your medicines, how you feel and your last result all change what a number means.
It doesn't remember.
Close this page and your results are gone. That's on purpose: nothing was ever sent to us.
We also make Vita: Health Coach, an app for those parts. It reads your whole report with your medicines and history in mind, answers follow-up questions in plain words, and keeps your reports in one place — for you and for the people you look after.
Vita: Health Coach on the App StoreSources
- ABIM — Laboratory test reference ranges (January 2026)
- Merck Manual Professional — Hypomagnesemia
- Northwestern Medicine — Laboratory critical values list (December 2025)
Stuck on a word? See the medical words. How we choose our sources. More about Vita Health Coach.