Is Magnesium useful for fatigue?

Magnesium is often marketed for fatigue, but the scientific evidence is mixed. Deficiency can indeed cause fatigue, especially in athletes or those with increased needs. However, supplementation in individuals with normal magnesium levels usually provides no additional benefit. Studies show only moderate improvement in exhaustion when deficiency is confirmed. The evidence for a general anti-fatigue effect is weak and often based on mechanistic assumptions or small studies. A blood test (serum magnesium, possibly RBC magnesium) is advisable before taking supplements. High doses can cause diarrhea. Overall: magnesium can help if deficient, but it is not a miracle cure for fatigue. Evidence is rated as 'mixed'.