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). Optimum is 6.0–6.5 mg/dL, not 4.2–6.8 that most labs use.
Which form to choose
- Glycinate — general use, sleep, anxiety (400 mg elemental)
- Malate — fatigue, fibromyalgia, daytime (300 mg)
- Citrate — constipation, fast absorption (200–400 mg)
- Threonate — cognition, crosses blood-brain barrier (2000 mg = 144 mg elem.)
- AVOID: magnesium oxide (< 4% absorption) — most common in pharmacies
Dosing
Start at 200 mg in the evening, increase to 400 mg. Higher doses (600–800 mg) only under medical supervision. In renal failure, consult a doctor first. Diarrhoea signals excess.
Scientific references