Magnesium levels: what's normal, high and low
A mineral involved in 300+ enzyme reactions, including muscle, nerve, and heart function.
Medically reviewed by Youmna DiStefano, MD · Last reviewed September 2026
The short answer
Magnesium is measured with a standard blood draw; no fasting is needed. A typical reference range is 1.70 – 2.20 mg/dL. At TestWell it's $19.99 all-in as Magnesium, results in 2–4 business days, drawn at Quest or Labcorp. An out-of-range result is a prompt to look closer, not a diagnosis.
- Units
- mg/dL
- Sample
- Blood draw
- Fasting
- Not required
- Results
- 2–4 business days
- Price
- $19.99
- Labs
- Quest or Labcorp · BioReference in NY/NJ
Magnesium Reference Range
These are the typical adult reference ranges used by major US labs. Your report will include the specific range used by the lab that processed your sample.
| Population | Range |
|---|---|
| age 18+ | 1.70 – 2.20 mg/dL |
Reference ranges are educational. Always interpret your result with the specific range printed on your lab report and discuss anything outside the range with a clinician.
Have a result in hand? analyze it with your AI assistant using these reviewed ranges, or run it through our explainer. Tools: look up another marker's range · convert lab units
What your Magnesium result may mean
Usually reflects supplement excess or kidney impairment.
What a high Magnesium means: causes, symptoms, next steps ↓Common in alcohol use, diuretic use, GI losses, or poor diet. Can cause muscle cramps and arrhythmias.
What a low Magnesium means: causes, symptoms, next steps ↓Educational only — not a diagnosis. Many factors can influence a single result. Discuss anything that concerns you with a healthcare provider.
What does a high Magnesium mean?
High magnesium (hypermagnesemia) is uncommon in people with normal kidneys. It's usually from magnesium-containing laxatives, antacids or supplements in someone with reduced kidney function, or from IV magnesium in a medical setting. Mild elevations cause few symptoms; higher levels cause weakness, low blood pressure and slowed heart rhythm.
Common causes of a high Magnesium
- Magnesium laxatives, antacids or high-dose supplements with reduced kidney function
- Chronic kidney disease
- Hypothyroidism, adrenal insufficiency, lithium (mild)
- Sample hemolysis (mild artifact)
Ordered from most to least common.
Symptoms that can go with it
- Nausea, flushing, weakness
- Low blood pressure, slow heartbeat, drowsiness when high
What clinicians usually check next
- Kidney function
- Stop magnesium-containing products
- Repeat
Can magnesium supplements cause a high level?
In healthy kidneys, rarely — excess is excreted. With reduced kidney function, yes, which is why supplements need care in kidney disease.
Educational only — not a diagnosis. A single result outside the range is a prompt to look closer with a clinician.
What does a low Magnesium mean?
Low magnesium is common and often missed: proton-pump inhibitors, diuretics, alcohol, diarrhea, poorly controlled diabetes and low intake are the usual causes. Because most magnesium is inside cells, a normal serum level doesn't exclude deficiency, but a low one confirms it. Low magnesium drags potassium and calcium down with it and causes cramps, palpitations and fatigue.
Common causes of a low Magnesium
- Proton-pump inhibitors (long-term), diuretics, some antibiotics and chemotherapy
- Alcohol use disorder
- Chronic diarrhea, malabsorption, bariatric surgery
- Poorly controlled diabetes (urinary loss)
- Low dietary intake
Ordered from most to least common.
Symptoms that can go with it
- Muscle cramps, twitches, weakness
- Palpitations
- Fatigue, poor sleep
- Numbness, tremor when more severe
What clinicians usually check next
- Potassium and calcium (often low together)
- Medication and alcohol review
- Kidney function
- Repeat after correcting the cause
Follow-up tests at TestWell: Calcium ($26.99).
Seek care promptly if
- Low magnesium with palpitations, an irregular pulse or seizures — same-day care
Can my magnesium be low even if the blood test is normal?
Yes — serum magnesium is about 1% of the body's total. A low result is meaningful; a normal one doesn't rule deficiency out when symptoms and risk factors fit.
Educational only — not a diagnosis. A single result outside the range is a prompt to look closer with a clinician.
How do you get a Magnesium test?
Order online, a licensed physician reviews the requisition, and you walk into a nearby lab for the draw. Magnesium is available on its own or inside these panels — panels cost less per marker when you want the fuller picture.
| Option | Includes | Price |
|---|---|---|
| Magnesium | This marker only | $19.99 |
| Fitness & Performance Panel | 8 tests | $119.99 |
| Sleep Health Panel | 8 tests | $129.99 |
| Vitamin & Mineral Deficiency Panel | 9 tests | $189.99 |
| Total Body Essentials Panel | 39 tests | $399.99 |
Quest vs. Labcorp for Magnesium: which lab should you pick?
Both are CLIA-certified national labs and the result is clinically equivalent, so pick whichever location is closer. Your report will print that lab's own reference range, which can differ slightly from the table above.
| Lab | Available | Price |
|---|---|---|
| Quest Diagnostics | Yes | $19.99 |
| Labcorp | Yes | $19.99 |
| BioReference (NY & NJ) | Yes | $20.99 |
Need help choosing a location? Use the lab finder to see draw sites near your ZIP.
Frequently asked
What does a high Magnesium mean?
High magnesium (hypermagnesemia) is uncommon in people with normal kidneys. It's usually from magnesium-containing laxatives, antacids or supplements in someone with reduced kidney function, or from IV magnesium in a medical setting. Mild elevations cause few symptoms; higher levels cause weakness, low blood pressure and slowed heart rhythm.
Can magnesium supplements cause a high level?
In healthy kidneys, rarely — excess is excreted. With reduced kidney function, yes, which is why supplements need care in kidney disease.
What does a low Magnesium mean?
Low magnesium is common and often missed: proton-pump inhibitors, diuretics, alcohol, diarrhea, poorly controlled diabetes and low intake are the usual causes. Because most magnesium is inside cells, a normal serum level doesn't exclude deficiency, but a low one confirms it. Low magnesium drags potassium and calcium down with it and causes cramps, palpitations and fatigue.
Can my magnesium be low even if the blood test is normal?
Yes — serum magnesium is about 1% of the body's total. A low result is meaningful; a normal one doesn't rule deficiency out when symptoms and risk factors fit.
Do I need a doctor's order to test my magnesium?
No. TestWell's licensed physician network reviews and approves your order — usually within minutes. You can place an order online without an in-person visit or a referral from your own doctor.
How long does it take to get Magnesium results?
Most Magnesium results are available in 1–3 business days after your specimen arrives at the lab. You'll get an email the moment your results are ready, with everything viewable in your TestWell portal.
How much does a Magnesium test cost?
Our Magnesium starts at $19.99. That's the all-in price — no copays, no insurance hoops, no surprise bills. HSA and FSA cards are accepted.
Do I need to fast before my Magnesium test?
Fasting is not required for the Magnesium test. You can have your blood drawn any time of day.
Which lab will process my Magnesium test?
Your test will be processed by Quest Diagnostics, Labcorp, or BioReference depending on which is closest to you and which lab carries the test. All three are CLIA-certified and trusted by hospitals nationwide. You'll choose your lab during checkout from 4,000+ locations.
What can throw off a Magnesium result?
Common medications and keto and high-protein diets can change a Magnesium result without anything being wrong. Common medications can lower Magnesium — check magnesium and B12 on long-term PPIs. Keto and high-protein diets can lower Magnesium — hydrate and mention the diet if a metabolic panel is drawn in the transition. Each is explained on our physician-reviewed "Before your test" pages; when one applies, remove it and retest.
Ready to test your magnesium?
Order in two minutes, get physician-approved, and visit a lab the same day. Starts at $19.99.