Magnesium: What It Does, How Much You Need, and How to Choose
Low magnesium quietly wrecks sleep, mood and muscles — and many people never check it. This mineral helps hundreds of enzyme reactions, supports normal nerve and muscle function, keeps your heartbeat steady, helps bones stay strong, and plays a role in blood sugar and blood pressure control.
Common signs of low magnesium include muscle cramps or twitches, trouble sleeping, unexplained fatigue, pins and needles, and irregular heartbeat. People at higher risk are older adults, those with type 2 diabetes or long-term stomach issues, people taking loop or thiazide diuretics, and heavy endurance athletes.
Food should come first. Choose magnesium-rich options like spinach (about 157 mg per cooked cup), pumpkin seeds (around 150 mg per ounce), black beans (about 120 mg per cup cooked), almonds (roughly 80 mg per ounce), brown rice (about 80 mg per cup cooked), a medium banana (≈32 mg), and a small square of dark chocolate (≈60 mg per ounce). A balanced plate with a few of these foods usually covers daily needs.
Supplements help when diet falls short. Common forms are magnesium citrate, glycinate, oxide, malate, and threonate. Glycinate is gentle on the gut and good for sleep or anxiety. Citrate absorbs well but can loosen stools — sometimes useful for constipation. Oxide has less absorbable magnesium and more digestive side effects for many people. Look for elemental magnesium on labels so you know the actual dose.
How much to take? Recommended daily amounts are about 400–420 mg for adult men and 310–320 mg for women from food and supplements combined. Health authorities set the upper limit for supplemental magnesium at 350 mg per day to avoid diarrhea and cramps, though therapeutic doses higher than that are used under medical supervision.
Watch for drug interactions and safety issues. Magnesium can bind to antibiotics like tetracyclines and fluoroquinolones, and to bisphosphonates — separate doses by at least two hours. If you have kidney disease, talk to your doctor before using supplements; impaired kidneys can cause dangerous magnesium buildup.
Testing magnesium isn't straightforward. Serum magnesium is easy to check but can look normal even when body stores are low. If you suspect deficiency, try a short supplement trial (4–8 weeks) while monitoring symptoms and discussing results with your clinician.
Practical tips: get most magnesium from food, pick glycinate for gentle effects or citrate if you need laxative action, split doses to cut stomach upset, take at night if you want better sleep, and always check interactions with prescription meds. If you're unsure, ask your healthcare provider for personalized advice.
Magnesium and vitamin D work together. Your body needs magnesium to activate vitamin D so low magnesium can blunt vitamin D benefits. If you take vitamin D supplements, check your magnesium intake from foods or supplements. Also think about timing: split high-dose calcium supplements away from magnesium if you notice stomach issues. Buying tip: go for third-party tested brands and compare elemental magnesium per pill to avoid surprise dosing today.
