Magnesium

Also called Mg, serum magnesium, or magnesium total.

An essential electrolyte involved in over 300 enzymatic reactions, including muscle function, nerve signalling, sleep regulation, and energy metabolism. One of the most under-tested nutrients in adults over thirty.

Test with Aniva Membership

How to test with Aniva

Sample type
Venous blood
Fasting required
No
Best timing
Morning, 7–11am
Results in
~7 days

What magnesium actually is and does for you

Magnesium is the fourth most abundant mineral in the human body and a cofactor in more than 300 enzymatic reactions. It regulates muscle and nerve function, blood glucose control, and blood pressure, and is required for protein synthesis and the production of ATP.

About sixty percent of the body's magnesium is stored in bone; the remainder is distributed across muscle tissue, soft tissue, and a small fraction (less than one percent) in blood serum.

Why it's worth checking.

Magnesium status is one of the more under-recognised drivers of fatigue, sleep disturbance, and muscle cramping in otherwise healthy adults. Subclinical deficiency is common, estimated to affect 10–30% of the population in industrialised countries, and is rarely caught in routine GP visits because magnesium is not part of a standard German Hausarzt blood panel.

Testing magnesium becomes particularly relevant for people with persistent muscle cramps, type 2 diabetes risk, chronic stress, restless sleep, or migraine patterns, and for athletes whose intake doesn't keep pace with sweat losses.

What your result tells you.

If your level is low: may indicate inadequate dietary intake, gastrointestinal losses, renal wasting, or refeeding effects. Low magnesium often coexists with low potassium and low calcium.

If your level is high: typically reflects impaired kidney function or excess supplementation. Mild elevations are common in people taking magnesium-based laxatives or antacids.

If your level is in range: a single normal reading does not rule out tissue depletion. If symptoms persist, intracellular or RBC magnesium can be a useful follow-up.

The reference range, by the numbers.

A reference range describes the values typically measured in a healthy adult population, not a verdict on whether you're well. Published by DGKL, reviewed every year.

Narrow target range
0.85–0.95 mmol/L
2.07–2.31 mg/dL
Within reference range
0.75–0.84 mmol/L
1.82–2.04 mg/dL
Just outside range
0.70–0.74 mmol/L
1.70–1.81 mg/dL
Below reference range
< 0.70 mmol/L
< 1.70 mg/dL
Above reference range
> 1.05 mmol/L
> 2.55 mg/dL

Things that can throw magnesium results off.

Recent supplementation: magnesium taken in the 24 hours before the draw can elevate serum levels and mask a true deficit. We recommend pausing supplementation 48 hours before testing.

Haemolysis: magnesium is concentrated inside red blood cells, so a haemolysed sample reads falsely high. Aniva clinics flag and re-draw any haemolysed samples automatically.

Diuretic use, PPIs, and alcohol: all increase renal magnesium loss and may produce true low readings even with adequate intake.

Magnesium is part of Aniva Full.

There's one way to test with us: become an Aniva member. One yearly check-in, 100+ markers including magnesium, in a single morning visit.

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Aniva liefert Gesundheitsinformationen, keine medizinischen Diagnosen. Die Ergebnisse ergänzen die Beratung durch Ihren Hausarzt, ersetzen diese jedoch nicht.

Where this information comes from.

We pull our reference ranges and content from accredited reference laboratories and peer-reviewed research — so you can check our work.

Guideline
DGKL Reference Intervals (2024)Deutsche Gesellschaft für Klinische Chemie — German clinical reference intervals for serum magnesium.
Reference lab
Mayo Clinic LaboratoriesTest catalog: Magnesium, Serum (TMAGS), 2025 edition.
Peer-reviewed
Volpe (2013)Magnesium in Disease Prevention and Overall Health. Advances in Nutrition, 4(3).
Peer-reviewed
de Baaij et al. (2015)Magnesium in Man: Implications for Health and Disease. Physiological Reviews, 95(1).
Gov agency
NIH Office of Dietary SupplementsMagnesium Fact Sheet for Health Professionals. Updated 2024.
Guideline
Endocrine SocietyClinical Practice Guideline on electrolyte disorders, 2023 update.
LOINC19123-9
MeSHD008274
WikidataQ11788
Lab codeMG

Questions people ask.

Do I need to fast before a magnesium test?+

No — fasting is not required for serum magnesium. We do recommend pausing magnesium-containing supplements for 48 hours before testing, since recent supplementation can artificially elevate serum levels and mask a deeper tissue deficit.

What's the difference between serum and RBC magnesium?+

Serum magnesium measures the small fraction circulating in blood plasma — tightly regulated and quick to test. RBC magnesium measures intracellular stores and is more sensitive to chronic depletion, but it's a less common assay. Aniva's standard panel uses serum; RBC is recommended as a follow-up if symptoms persist despite a normal serum reading.

How does magnesium affect sleep?+

Magnesium regulates GABA, the primary inhibitory neurotransmitter, and supports melatonin synthesis. Low magnesium is associated with restless sleep, frequent night-waking, and reduced sleep efficiency in observational studies.

Should I test if my GP already ran bloods?+

Magnesium is not part of a standard German Hausarzt panel (großes Blutbild) and is rarely included unless specifically ordered. If your GP didn't request it, it almost certainly wasn't tested — even if other electrolytes were measured.

How often should I retest magnesium?+

For people with normal results: annually as part of the Aniva membership baseline. For people with borderline or low results who have started intervention: 8–12 weeks after starting supplementation or dietary change, to confirm the change has taken effect.

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