Magnesium
Supports muscles, nerves, heartbeat, blood sugar and blood pressure; helps make energy and activate vitamin D.
If you are short of it
Possible signs
- Muscle cramps or twitching
- Muscle weakness
- Tiredness, low energy
- Palpitations (fast heartbeat)
- Low mood or irritability
- Restless legs, poor sleep
- Tingling or numbness in hands and feet
- Poor appetite
These signs are common and have many other causes. They are clues, not proof; a blood test and a doctor can tell.
Who is more at risk
Type 2 diabetes, alcohol use, long-term acid reducers or water pills, chronic diarrhoea, older adults.
Foods rich in Magnesium
| Food | Serving | Amount | women 19–50 | men 19–50 |
|---|---|---|---|---|
| Pumpkin seeds | a small handful (28 g) | 156 NIH | 50% | 39% |
| Quinoa | 1 cup cooked | 118 | 38% | 30% |
| Mackerel | 100 g cooked | 97 | 31% | 24% |
| Mung beans | 1 cup cooked | 97 | 31% | 24% |
| Black-eyed peas (lobia) | 1 cup cooked | 91 | 29% | 23% |
| Brown rice | 1 cup cooked | 84 NIH | 27% | 21% |
| Almonds | a small handful (28 g) | 80 NIH | 26% | 20% |
| Chickpeas | 1 cup cooked | 79 | 25% | 20% |
| Spinach (cooked) | ½ cup (90 g) | 78 NIH | 25% | 20% |
| Kidney or white beans | 1 cup cooked | 74 NIH | 24% | 19% |
| Cashews | a small handful (28 g) | 74 NIH | 24% | 19% |
| Fava beans (foul) | 1 cup cooked | 73 | 24% | 18% |
| Lentils | 1 cup cooked | 71 | 23% | 18% |
| Dark chocolate (70% or more) | 30 g, about 3 squares | 65 | 21% | 16% |
Unit: mg. Share of the daily amount. Values marked NIH were checked against the food tables of the NIH Office of Dietary Supplements; the others are approximate and unchecked. Real foods vary with variety, brand, soil and cooking.
As a supplement
Citrate, glycinate or malate are well absorbed; oxide is cheap but acts as a laxative. Take with food or in the evening.
Too much
Above 350 mg a day from supplements causes diarrhoea and cramps. People with kidney disease can build up dangerous levels — ask a doctor first.
How much you need each day
| Group | Recommended | Upper limit |
|---|---|---|
| Infants 0–6 months | 30 | — |
| Infants 7–12 months | 75 | — |
| Children 1–3 years | 80 | 65 |
| Children 4–8 years | 130 | 110 |
| Children 9–13 years | 240 | 350 |
| Boys 14–18 years | 410 | 350 |
| Girls 14–18 years | 360 | 350 |
| Men 19–30 years | 400 | 350 |
| Women 19–30 years | 310 | 350 |
| Men 31–50 years | 420 | 350 |
| Women 31–50 years | 320 | 350 |
| Men 51–70 years | 420 | 350 |
| Women 51–70 years | 320 | 350 |
| Men over 70 | 420 | 350 |
| Women over 70 | 320 | 350 |
| Pregnant 14–18 years | 400 | 350 |
| Pregnant 19–30 years | 350 | 350 |
| Pregnant 31–50 years | 360 | 350 |
| Breastfeeding 14–18 years | 360 | 350 |
| Breastfeeding 19–30 years | 310 | 350 |
| Breastfeeding 31–50 years | 320 | 350 |
Unit: mg. Upper limit applies to magnesium from supplements and medicines, not food. US/Canada Dietary Reference Intakes (National Academies), as summarised by the NIH Office of Dietary Supplements. Other countries’ values differ slightly. These are amounts for healthy people, not treatment doses.
Interactions
Take care · Calcium
High doses of calcium and magnesium compete for absorption. Split them: for example calcium with lunch and magnesium in the evening.
Works together · Vitamin D
Magnesium is needed to activate vitamin D, so low magnesium can blunt the effect of vitamin D.
Works together · Vitamin B6 (pyridoxine)
B6 and magnesium are often combined in supplements and used together in the body.
Medicines and habits to mention to your doctor
Levothyroxine (thyroid hormone)
Take it alone on an empty stomach and wait about 4 hours before calcium, iron or magnesium supplements.
Tetracycline, doxycycline, ciprofloxacin, levofloxacin
Minerals bind these antibiotics. Usually take the antibiotic 2 hours before or 4–6 hours after the supplement or dairy; check the leaflet.
Acid reducers (omeprazole, esomeprazole, famotidine)
Long-term use lowers absorption of B12, iron, magnesium and calcium carbonate. Calcium citrate is a better choice; ask about monitoring.
Water pills (furosemide, thiazides)
Furosemide-type pills wash out magnesium, zinc, thiamin and calcium. Thiazides raise blood calcium, so calcium plus vitamin D supplements need a doctor’s check.
Osteoporosis tablets (alendronate and similar)
Take on an empty stomach with plain water and wait 30–60 minutes before food, calcium or other supplements.
Digoxin (heart)
High calcium or low magnesium can affect heart rhythm with digoxin. Do not start calcium, vitamin D or magnesium without asking.
Regular alcohol
Alcohol blocks absorption and increases loss of thiamin, folate, B6, magnesium and zinc.
Page updated: 2026-10-08 · By Prof. E. Shalaan, Applied Sciences and AI (ASAI)