Magnesium is the body's fourth most common mineral and is needed in over 300 enzyme reactions: for the muscles to relax after contracting (calcium contracts, magnesium releases), for the nerves' signals, for energy metabolism in every cell, for the heart's rhythm, for blood sugar and blood pressure, and as a building block in the skeleton, where half the body's magnesium is found. Only one percent is in the blood, which is why an ordinary blood test (serum magnesium) can be normal although the cells and skeleton are deficient; the body keeps the blood level stable at the expense of the stores. The recommended intake is around 350 mg a day for men and 300 mg for women, and many people fall short, since magnesium is in the foods we eat too little of: wholegrains, legumes, nuts, seeds, leafy greens and dark chocolate. At the same time magnesium is sold as a solution to almost everything, and most people who take it are neither deficient nor helped by it. This guide covers the symptoms of deficiency, who gets it, how to know, what research actually says about magnesium for cramps, sleep, stress, migraine and PMS, which type and dose, side effects and warnings, magnesium in food, and how cupping and stretching release cramping muscles. For calf cramps specifically, see calf cramps.
Symptoms of magnesium deficiency
- Muscles: cramps (calves, feet, toes, hands), muscle twitches (eyelid, muscle fibres that "flutter"), tension, stiffness, weakness, tremor.
- Nerves and mind: tiredness, lack of energy, anxiety, irritability, low mood, sleep problems, concentration difficulties, increased stress sensitivity, numbness and tingling.
- Heart: palpitations, extra beats, in severe deficiency rhythm disturbances.
- Other: headache and migraine, constipation, loss of appetite, nausea, PMS symptoms, increased sensitivity to sound, in severe deficiency seizures and confusion.
Mild deficiency only gives the first symptoms, and they are unspecific: cramps, tiredness, anxiety and sleep problems have ten other common causes (iron deficiency, vitamin D deficiency, thyroid, stress, sleep deprivation, dehydration, medicines). What points to magnesium is the combination of muscle cramps or twitches, palpitations and tiredness in someone in a risk group.
Who gets magnesium deficiency, and why
| Group | Why |
|---|---|
| Gut problems: coeliac disease, Crohn's, ulcerative colitis, IBS with diarrhoea, gastric surgery, chronic diarrhoea | Poorer absorption in the small intestine and losses through the gut |
| Acid blockers (omeprazole and similar) for more than a year | Inhibit absorption; a well-known and underdiagnosed cause, regulators recommend checking with long-term use |
| Diuretics (furosemide, thiazides), certain antibiotics, chemotherapy, ciclosporin | Increased excretion via the kidneys |
| Type 2 diabetes and insulin resistance | High blood sugar pulls magnesium out via the urine; one in three diabetics is deficient, and the deficiency worsens blood sugar further |
| High alcohol intake | Increased excretion, poorer diet, vomiting and diarrhoea; deficiency in a majority with alcohol dependence |
| Hard and prolonged training, heavy sweating | Losses via sweat and urine, increased need; endurance athletes in heat |
| Poor or one-sided diet: white bread, few greens, few legumes and nuts, low-calorie diet, eating disorder, elderly with small portions | Intake doesn't meet the need |
| Pregnant and breastfeeding women | Increased need; magnesium for pregnancy cramps has some support |
| The elderly | Poorer absorption, more medicines, less food |
| Prolonged stress | Stress hormones increase excretion, and low magnesium increases stress sensitivity; a vicious circle that is documented but often exaggerated in marketing |
How to know if you are deficient
Serum magnesium (blood test) under 0.7 mmol/l is deficiency, but a normal value doesn't rule out deficiency in the cells; the test mainly catches severe deficiency and is taken with risk factors such as acid blockers, diarrhoea, diabetes, diuretics and alcohol, and with unexplained palpitations, cramps or low calcium and potassium (which don't correct without magnesium). There are no good and accessible measures of cellular magnesium; red blood cell and hair magnesium are sold privately but poorly validated. In practice three things decide: are you in a risk group, do you have symptoms that fit, and do the symptoms disappear on a trial treatment with 300–400 mg a day for four to six weeks? If the cramps, twitches and palpitations disappear it is reasonable to continue; if nothing happens in six weeks magnesium wasn't the cause, and continuing is a waste. Ask your doctor for a test if you have diarrhoea, take acid blockers or diuretics, have diabetes, or have unexplained palpitations.
Magnesium for cramps, sleep, stress, migraine and PMS: what actually has support
| For | What research says |
|---|---|
| Nocturnal leg cramps | In the elderly without deficiency: no effect in several well-made studies (Cochrane). In pregnant women: some effect. With real deficiency: helps. Calf stretching in the evening, fluids and movement have better support against cramps in healthy people |
| Muscle cramps during exercise | Usually due to fatigue in the muscle and nervous system, not magnesium; fluids and salt when sweating, warm-up and stretching help more |
| Sleep | Small studies on elderly people with sleep problems and low levels show slightly shorter time to fall asleep; in people without deficiency the effect is small or none. Reasonable to try 300 mg in the evening for four weeks, not as a replacement for sleep routines, see sleep problems |
| Stress, anxiety, low mood | Some effect on self-rated anxiety in people with low levels or high stress; moderate evidence; doesn't replace sleep, movement and stress management, see stress |
| Migraine | Yes, preventively: 400–600 mg a day reduces the number of attacks in many, recommended in international guidelines; takes two to three months. See migraine |
| PMS | Yes, moderately: less fluid retention, mood swings and breast tenderness in some studies, especially together with B6. See PMS |
| Constipation | Yes: magnesium oxide and magnesium citrate draw fluid into the gut and are proven laxatives |
| Blood pressure, blood sugar, heart | Small reductions in blood pressure and improved blood sugar in people with deficiency or diabetes; no effect in healthy people with normal intake. Dietary magnesium (not supplements) is linked in population studies to lower risk of heart disease |
| Restless legs | Weak evidence; iron (ferritin) is what should be checked first, see restless legs |
| Bones | Adequate intake through diet matters for bone density; supplements beyond that add nothing |
| Performance, fat burning, "detox", skin | No support |
Which type, which dose, and when
- Type: magnesium citrate (good absorption, mildly laxative, good for constipation and as all-round), magnesium glycinate/bisglycinate (good absorption, gentle on the stomach, preferred in the evening and for anxiety), magnesium malate (good absorption, neutral), magnesium taurate and orotate (marketed for the heart, no particular support), magnesium L-threonate (marketed for the brain based on animal studies, expensive, nothing established in humans), and magnesium oxide (cheapest, most common in effervescent tablets and many pharmacy products, but only a few percent is absorbed; works as a laxative, poorly as a supplement). Choose citrate or glycinate.
- Dose: 200–400 mg magnesium (elemental, read the label: "magnesium citrate 1,500 mg" may contain 250 mg magnesium) a day from supplements; over 350 mg from supplements can cause diarrhoea. For migraine prevention 400–600 mg. Preferably split into two doses for better absorption.
- When: with food (better absorption, kinder to the stomach); in the evening if you take it for sleep or cramps. Not at the same time as levothyroxine, certain antibiotics (tetracyclines, quinolones), bisphosphonates or iron; keep two to four hours apart.
- How long: a four- to six-week trial; with effect and a risk factor that remains, continue; without effect, stop.
- Magnesium spray, baths and oil through the skin have no proven absorption; a warm bath with Epsom salt is pleasant for sore muscles, but the magnesium makes no difference.
Side effects, and when not to take magnesium
Most common are loose stools and diarrhoea (dose-dependent, less with glycinate), nausea and stomach cramps. Magnesium is safe for healthy kidneys, since the excess is passed in urine, but with reduced kidney function (kidney failure, elderly people with low GFR, some diabetics) the level can become dangerously high: tiredness, low blood pressure, slow pulse, muscle weakness; don't take it without a doctor. Talk to your doctor with heart disease with rhythm disturbance, myasthenia gravis, and if you take diuretics, heart medicines, antibiotics or bisphosphonates. Pregnant women can take up to 300–350 mg. Children get smaller doses by weight. Magnesium doesn't fix cramps, sleep problems or anxiety that are due to something else, and should not delay an investigation of palpitations, numbness or tiredness that doesn't pass.
Magnesium in food
Pumpkin seeds (about 500 mg per 100 g), sunflower seeds, sesame and tahini, chia seeds, almonds, cashews, Brazil nuts, dark chocolate (70 percent and above, about 230 mg per 100 g), beans, lentils, chickpeas, tofu, wholegrain bread, oats, quinoa, brown rice, spinach, chard, kale, avocado, banana, and oily fish. Mineral water can give 20–100 mg per litre. Phytates in wholegrains and legumes inhibit absorption somewhat (soaking helps), and a lot of calcium, alcohol and sugar increase losses. Two tablespoons of pumpkin seeds, a handful of almonds and a portion of beans a day cover most of the need, and dietary magnesium is what is linked in studies to better heart health, not the tablets.
Tight and cramping muscles: cupping and stretching regardless of magnesium
A muscle that cramps or tenses almost always has a local problem: it is tired, short, poorly perfused or overloaded, and magnesium alone doesn't fix that. Calf stretches against a wall for 30 seconds in the evening, enough fluids and salt when sweating, a warm-up before training, and daily movement are what actually reduce cramps. Cupping increases blood flow in the muscle several times over, lifts the superficial fascia that binds the muscle, and releases tight bands in a few minutes: draw the dynamic cup with oil slowly along the calf from the heel towards the back of the knee, along the back and front of the thigh, and across the shoulders, five minutes per area, followed by stretching; leave static cups for two to three minutes on the sorest point. Do it in the evening if the cramps come at night; in the middle of a cramp it helps to stretch the muscle (pull the toes towards you with a calf cramp) and then cup lightly once the cramp has released. With cramps that come daily, at rest, in several muscle groups at once or with weakness and numbness: a doctor. More in muscle knots and trigger points.
Read more
Calf cramps, sleep problems, stress, migraine, iron deficiency, vitamin D deficiency, palpitations, and sluggish bowels.
Frequently asked questions
What are the symptoms of magnesium deficiency?
Muscle cramps and twitches (calves, feet, eyelid), tension and stiffness, tiredness, anxiety, irritability, sleep problems, palpitations and extra beats, numbness, headache and constipation; in severe deficiency rhythm disturbances and seizures. The symptoms are unspecific and shared with iron deficiency, vitamin D deficiency, thyroid disorder, stress and sleep deprivation, so the combination with a risk factor (gut problems, acid blockers, diabetes, diuretics, alcohol, hard training) is what points to magnesium.
How do you know if you are magnesium deficient?
The blood test (serum magnesium under 0.7) only catches severe deficiency, since almost all magnesium is in cells and bone and the blood is kept stable at the expense of the stores. In practice: are you in a risk group, do the symptoms fit, and do they disappear on four to six weeks of trial treatment with 300–400 mg a day? If nothing happens in six weeks, magnesium wasn't the cause. Ask for a test with diarrhoea, acid blockers, diuretics, diabetes or unexplained palpitations.
Does magnesium help with leg cramps at night?
In the elderly without deficiency: no, according to several well-made studies; in pregnant women: somewhat; with real deficiency: yes. Against ordinary nocturnal calf cramps, calf stretching for 30 seconds in the evening, enough fluids, movement during the day and cupping of the calf have better support. By all means try magnesium for six weeks, but don't continue if the cramps haven't decreased.
Which type of magnesium is best, and how much should you take?
Magnesium citrate (all-round, mildly laxative) or magnesium glycinate (gentle, good in the evening); avoid magnesium oxide, which is cheapest but poorly absorbed and mostly works as a laxative. 200–400 mg magnesium a day (elemental, read the label), with food, preferably split into two doses; for migraine prevention 400–600 mg. Keep apart from levothyroxine, iron and certain antibiotics. Spray, oil and baths through the skin have no proven absorption.
What should you consider before taking magnesium?
That it is safe for healthy kidneys but dangerous with reduced kidney function (ask your doctor if you have kidney disease, are elderly or have diabetes with kidney involvement), that loose stools are the most common side effect, that it should not be taken at the same time as levothyroxine, iron, bisphosphonates and certain antibiotics, and that it should not replace an investigation of palpitations, numbness, cramps at rest or tiredness that doesn't pass. What has the best support is migraine prevention, PMS, constipation and deficiency in risk groups, not general tiredness in healthy people.
Written by Curam. Last updated 17 October 2026. This is general self-care information and does not replace medical care. For sudden, severe or unusual symptoms, contact your doctor. Talk to your doctor before cupping if you are pregnant, take blood thinners or have a condition affecting skin, blood vessels or blood.
