How to test with Aniva
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.
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.
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.
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.
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We pull our reference ranges and content from accredited reference laboratories and peer-reviewed research. You can check our work.
FAQ
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.
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.
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.
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.
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.
