Magnesium deficiency: symptoms, tests and which form to choose
Dr Sergey Saadi
About 50% of Europeans consume less magnesium than the recommended daily intake. Chronic subclinical deficiency is one of the most commonly undiagnosed metabolic problems – because serum magnesium only flags a deficiency once intracellular levels have already dropped substantially.
Why magnesium is critical
Magnesium is a cofactor in > 300 enzymatic reactions: ATP production, DNA synthesis, calcium and potassium balance, insulin signalling. DiNicolantonio et al. (Open Heart, 2018) call subclinical magnesium deficiency an underrated driver of cardiovascular disease.
Symptoms
- Muscle cramps (especially at night), eyelid twitch
- Fatigue, low stress tolerance
- Insomnia, difficulty falling asleep
- Palpitations, ectopic beats
- Constipation
- Headaches and migraine
- PMS and painful periods
- High blood pressure
Tests
Serum magnesium reflects only 1% of total body magnesium. Better: RBC magnesium (red blood cell). The literature discusses 6.0–6.5 mg/dL as more favourable, while lab reference ranges are wider (4.2–6.8); this is an educational, not a diagnostic, cutoff.
Which form to choose
- Glycinate – studied in the context of sleep and anxiety
- Malate – studied in fatigue and fibromyalgia
- Citrate – well absorbed, also affects bowel function
- Threonate – studied in the context of cognition
- AVOID: magnesium oxide (< 4% absorption) – most common in pharmacies
Dosing
Dose and form are chosen by a doctor, based on tests, symptoms, medications and kidney function. Do not start on your own with kidney disease or cardiac medication. Diarrhoea is the first sign of excess.
Scientific references