# Magnesium: A mineral your muscles and heart rhythm need

> Magnesium helps your muscles, nerves and heart rhythm. Check your result, see what low and high levels mean, and why a normal level can still miss low stores.

- Also called Serum magnesium and Mg
- Not on a standard checkup
- No fasting needed
- Web page: https://picardo.health/guides/biomarkers/magnesium

## The short answer

Magnesium helps your muscles, nerves and heart rhythm work. Less than 1% of it is in your blood, so a normal result can’t rule out low stores in your body.[1]

- **A good result:** 1.6 to 2.3 mg/dL, Labcorp’s range.[3]
- **If yours is low:** Common causes are acid-reducers taken for over a year, water pills, heavy drinking and diarrhea. Low magnesium can drag potassium and calcium down too.[1][8]
- **Should you test?** Worth it if you’ve taken an acid-reducer for over a year or take a strong water pill. Also if you have diabetes, a gut condition or low potassium or calcium that’s hard to fix.[1][2]

## What is a normal magnesium level?

Labcorp’s range is 1.6 to 2.3 mg/dL.[3] Outside it, this is how far off you are:[1][8]

| Result (mg/dL) | What it means |
| --- | --- |
| Under 1.3 | Very low: get medical advice today |
| 1.3 to 1.5 | Low: find the cause |
| 1.6 to 2.3 | Normal |
| 2.4 to 4.1 | Higher than the lab range |
| 4.2 or more | Very high: see a clinician today |

### Very low: get medical advice today

**Range:** Under 1.3 mg/dL.

Below about 1.25, low magnesium is severe. It can cause tremor, muscle spasms, seizures and abnormal heart rhythms.[8]

**How worried to be:** Get medical advice today. If you have spasms, a seizure or palpitations, go to an emergency department now.

**What to do next:**

1. Take a list of your medicines, especially acid-reducers and water pills.[1]
2. Ask for potassium and calcium to be checked too. They’re hard to correct until magnesium is.[8]

### Low: find the cause

**Range:** 1.3 to 1.5 mg/dL.

This is below Labcorp’s range.[3] The usual causes are acid-reducers taken for over a year, water pills, heavy drinking, diabetes and long-lasting diarrhea.[1][8]

**How worried to be:** Not urgent if you feel well. See a clinician in the next few weeks.

**What to do next:**

1. If you’ve taken an acid-reducer such as omeprazole for over a year, ask whether you still need it. In a quarter of the cases the FDA reviewed, magnesium only recovered once it stopped.[1]
2. Check potassium and calcium, which low magnesium can pull down.[1][8]
3. Ask whether a supplement makes sense. Citrate and chloride forms are absorbed better than oxide.[1]

[Test potassium and calcium, $4.00](https://app.picardo.health/labs/order?tests=322000&ref=guide-magnesium)

### Normal

**Range:** 1.6 to 2.3 mg/dL.

Your blood level is normal.[3] But under 1% of your magnesium is in your blood, so this can’t rule out low stores.[1] Some references put the bottom of normal a little higher, at about 1.8, so a 1.6 or 1.7 is worth rechecking if you have a reason to run low.[1][8]

**How worried to be:** Nothing to worry about.

**What to do next:**

1. If you have a reason to run low, such as long-term acid-reducers, eat magnesium-rich foods. Leafy greens, beans, nuts, seeds and whole grains are good sources.[1]

### Higher than the lab range

**Range:** 2.4 to 4.1 mg/dL.

In people with healthy kidneys this is uncommon. It usually means reduced kidney function, often together with magnesium from laxatives, antacids or supplements.[1][2] A damaged sample can raise it too, because red blood cells hold more magnesium than serum.[2]

**How worried to be:** Not urgent if you feel well. Recheck within a few weeks.

**What to do next:**

1. Stop magnesium supplements, laxatives and antacids until you’ve rechecked.
2. Check your kidney function, which a metabolic panel includes.[2]

[Test kidney function, $4.00](https://app.picardo.health/labs/order?tests=322000&ref=guide-magnesium)

### Very high: see a clinician today

**Range:** 4.2 mg/dL or higher.

Above about 4.2, too much magnesium starts to cause symptoms, such as low blood pressure, nausea, flushing and drowsiness. Higher still, it can cause weakness, trouble breathing and heart rhythm problems.[1]

**How worried to be:** See a clinician today. If you’re very weak, drowsy or short of breath, go to an emergency department now.

**What to do next:**

1. Stop all magnesium-containing products, including laxatives and antacids.
2. Take a list of your medicines and supplements with you.

## What is magnesium?

> Think of the blood test as a look into the lobby of a tall building. Almost all your magnesium is upstairs, in your bones and cells. The lobby can look normal while the floors above are running low.

Your body uses magnesium in over 300 chemical reactions, including those that run your muscles, nerves and heartbeat.[2] An adult holds about 25 g, half or more of it in bone. Less than 1% is in your blood, and your body keeps that level tightly controlled.[1]

## Can a blood test show if you’re low in magnesium?

Only partly. Blood levels have little to do with how much magnesium is in your body or your tissues, and no test of body stores is considered reliable.[1]

Some researchers, citing studies that link lower levels to disease, argue the bottom of the normal range should be higher, at about 2.1 mg/dL (0.85 mmol/L).[4] Kidney researchers have pushed back: that cutoff would label about half of people as deficient, and no trials show that raising magnesium above it helps.[5]

## What causes low magnesium?

- Acid-reducers (proton pump inhibitors) taken for more than a year[1]
- Water pills (loop and thiazide diuretics)[1]
- Heavy drinking[1][8]
- Type 2 diabetes, especially when blood sugar runs high[1][8]
- Crohn’s disease, celiac disease and long-lasting diarrhea[1][8]
- Some medicines, including the chemotherapy drug cisplatin, aminoglycoside antibiotics and cyclosporine[2][8]
- Older age[1]

## How to raise magnesium

- **Changing the medicine behind it:** Long-term acid-reducers and water pills are common causes. In a quarter of the cases the FDA reviewed, magnesium only recovered once the acid-reducer stopped.[1] How much it helps: a lot. How sure we are: fairly sure.
- **Magnesium supplements:** Keep to 350 mg a day unless a clinician advises more; above that, diarrhea is common. Citrate and chloride are absorbed better than oxide. With kidney disease, take them only on a clinician’s advice.[1] How much it helps: some. How sure we are: fairly sure.
- **Magnesium-rich food:** Leafy greens, beans, nuts, seeds and whole grains.[1] How much it helps: a little. How sure we are: fairly sure.

## Does magnesium help sleep, blood pressure or migraines?

A little, for some people:

- **Blood pressure.** In a 2025 analysis of 38 trials, supplements lowered blood pressure by about 3/2 mmHg on average, though results varied a lot between trials. The effect was clearest in people already treated for high blood pressure or low in magnesium, and there was no clear effect with normal blood pressure.[6]
- **Sleep.** A 2026 review of 12 trials found only low- to very-low-certainty evidence and didn’t support magnesium as a routine treatment for insomnia.[9]
- **Migraine.** US neurologists once rated magnesium as probably effective for preventing migraine.[1] Their 2026 guideline covers prescription medicines and doesn’t assess it.[7]

## Who should get a magnesium test?

It isn’t on the standard metabolic panel. It’s worth checking if:

- You’ve taken an acid-reducer for over a year.[1]
- You take a loop diuretic or a high-dose thiazide water pill.[2]
- Your potassium or calcium is low and hard to correct.[2][8]
- You drink heavily, or have diabetes, Crohn’s or celiac disease.[1]
- You have kidney disease and take magnesium-containing laxatives or antacids.[1]

## How to get a magnesium test, and what it costs

A magnesium test costs $3.25 through Picardo.

- [Magnesium on its own, $3.25](https://app.picardo.health/labs/order?tests=001537&ref=guide-magnesium). Labcorp 001537, no fasting needed.

Every order comes with:

- Results in 2 to 3 days, in the app
- Physician follow-up if you want one
- Free Labcorp draw, or $75 at home
- No other fees. HSA and FSA eligible.

It’s also part of the [Base Core Annual – Men](https://picardo.health/labs/panels/base-core-men), [Base Core Annual – Women](https://picardo.health/labs/panels/base-core-women), [Heart Health](https://picardo.health/labs/panels/heart-health), [Brain Health Screening](https://picardo.health/labs/panels/brain-health), [Fertility](https://picardo.health/labs/panels/fertility) and [Celiac / GI](https://picardo.health/labs/panels/celiac-gi) panels, if you’d rather test more at once.

Already have a result? [Ask Picardo about it](https://app.picardo.health/auth).

## Questions people ask

### Should I take magnesium if my blood level is normal?

Only if you have a reason to, such as a diet low in magnesium or a medicine that drains it. Food is the best source. If you take a supplement, keep it to 350 mg a day unless a clinician advises more; above that, diarrhea is common. With kidney disease, take it only if a clinician advises it, because your kidneys can’t clear the extra.[1]

### Is red blood cell magnesium a better test?

It’s sometimes promoted as one, but no test of magnesium stores is considered reliable, red blood cell magnesium included.[1]

### Can low magnesium cause low potassium?

Yes. Low magnesium can pull down both potassium and calcium, and they’re hard to correct until magnesium is back up.[1][8]

### Do acid-reducers lower magnesium?

They can, usually after more than a year of use. The FDA warned about it in 2011 and advised checking magnesium before and during long-term use. In a quarter of the cases it reviewed, supplements didn’t help and the acid-reducer had to stop.[1]

### Do I need to fast for a magnesium test?

No. A damaged (hemolyzed) sample can read falsely high, though, so a surprising high result is worth repeating.[2]

## Often checked alongside

- [Potassium](https://picardo.health/guides/biomarkers/potassium.md): A salt your heart and muscles depend on
- [Calcium](https://picardo.health/guides/biomarkers/calcium.md): Calcium in your blood, set by the parathyroid glands
- [Vitamin D](https://picardo.health/guides/biomarkers/vitamin-d.md): How much vitamin D you have stored
- [Creatinine](https://picardo.health/guides/biomarkers/creatinine.md): Muscle waste the kidneys filter out

## Test details

- **Labcorp test:** Magnesium, 001537
- **LOINC:** 19123-9
- **Sample:** Blood
- **Fasting:** Not needed
- **Typical lab range:** 1.6 to 2.3 mg/dL[3]
- **Units:** mg/dL in the US. For mmol/L, divide by 2.43.

## Sources

1. Office of Dietary Supplements, National Institutes of Health. Magnesium: fact sheet for health professionals. Updated January 6, 2026. https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/
2. Labcorp. Magnesium, test 001537. Labcorp test menu. Accessed October 28, 2026. https://www.labcorp.com/tests/001537/magnesium
3. Labcorp. Magnesium, test 001537. Sample report. Accessed October 28, 2026. https://files.labcorp.com/testmenu-d8/sample_reports/001537.pdf
4. Costello RB, Elin RJ, Rosanoff A, et al. Perspective: the case for an evidence-based reference interval for serum magnesium: the time has come. Adv Nutr. 2016;7(6):977–993. https://doi.org/10.3945/an.116.012765
5. de Baaij JHF, Bockenhauer D, Claverie-Martin F, et al. Comment to “Recommendation on an updated standardization of serum magnesium reference ranges”. Eur J Nutr. 2022;61(8):4231–4233. https://doi.org/10.1007/s00394-022-03004-9
6. Argeros Z, Xu X, Bhandari B, et al. Magnesium supplementation and blood pressure: a systematic review and meta-analysis of randomized controlled trials. Hypertension. 2025;82(11):1844–1856. https://doi.org/10.1161/HYPERTENSIONAHA.125.25129
7. Potrebic S, Tanveer S, Becker WJ, et al. Pharmacologic treatment for migraine prevention in adults practice guideline recommendations: report of the AAN Guidelines Subcommittee and the American Headache Society. Neurology. 2026;107(7):e214881. https://doi.org/10.1212/WNL.0000000000214881
8. Lewis JL III. Hypomagnesemia. Merck Manual Professional Edition. Updated June 2025. https://www.merckmanuals.com/professional/endocrine-and-metabolic-disorders/electrolyte-disorders/hypomagnesemia
9. Lopresti AL, Smith SJ, Drummond PD. Magnesium supplementation for sleep in adults: a systematic review of randomized controlled trials. J Diet Suppl. 2026;23(5):553–581. https://doi.org/10.1080/19390211.2026.2719670

Updated 2026-10-28. This is general health information, not medical advice: talk to your clinician about your results and before changing any treatment.