How to Take Magnesium Supplements

Learn all you need to know about taking magnesium supplements – the right dosage for different conditions, how much magnesium is too much and what kind of interactions magnesium has with other supplements, herbs and prescription medications.

Dosage – How Much Magnesium Should You Take

The standard dose for magnesium supplements is between 200 and 400mg of magnesium daily. Most magnesium supplements fall within this limit; however, you can also find supplements with higher dosages per pill.

Recommended Daily Allowances (RDA) for Magnesium

For Adults:

  • Men: 400mg per day
  • Women: 300 mg per day
  • Pregnant women: 350 mg per day
  • Breastfeeding mothers: 320 mg per day

For Children:

  • From birth to 3 years: 30 to 80 mg per day
  • From 4 to 8 years: 130 mg per day
  • From 9 to 13 years: 240 mg per day
  • From 14 to 18 years: 410 for boys, 360 for girls

These recommended amounts include magnesium that you get from different sources – food, medications and dietary supplements.

Safe Upper Intake Levels for Magnesium Supplements

Magnesium that you consume by eating magnesium rich food hasn't been linked to any adverse effects, so you don't have to be careful how much magnesium you get from food.

Magnesium from supplements and medication, on the other hand, may cause problems if you consume too much of it. That is why a safe upper intake level has been set. It differs according to age groups:

  • Babies up to 1 year: Not established
  • Children 1 to 3 years:  65 mg per day
  • Children 4 to 8 years: 110 mg per day
  • Children 9 years and up and adults: 350 mg per day

Stay within these limits as magnesium in larger doses can cause side effects, such as abdominal pain and diarrhea. If you consume extremely high doses of magnesium, it can cause irregular heartbeats and may even lead to cardiac arrest.

Dosage of Magnesium for Magnesium Deficiency

People with magnesium deficiency generally take magnesium supplements by mouth. If the deficiency is severe, the magnesium can also be delivered intravenously.

The doses for magnesium deficiency vary between individuals and depend on the severity of the condition. For mild hypomagnesemia, the dose can start at 500mg of magnesium chloride taken once a day. For severe magnesium deficiency, the dose can be as high as 4 grams of magnesium chloride given within a couple of hours.

Magnesium for Constipation (as Laxative)

Magnesium is the main ingredient in some laxatives. Milk of Magnesia, for example, provides 500 mg of magnesium hydroxide per tablespoon. People take as much as 4 tablespoons per day, which is way above the recommended daily amounts for adults. However, much of the magnesium is not absorbed as it is rapidly eliminated from the intestines (due to the laxative effect of the medication). 

You shouldn't use laxatives with magnesium on a regular basis. Take them only from time to time and make sure that you drink plenty of water when you do.

For Heartburn and Indigestion

Magnesium can be found in some remedies for heartburn and indigestion. Typically it is either in the form of magnesium oxide, magnesium hydroxide or magnesium carbonate. The doses used for heartburn vary; most often the medications contain up to 100mg of magnesium per tablet.

The total daily doses used for heartburn have been up to 1.000mg of magnesium hydroxide.

Magnesium for Headaches and Migraines

Magnesium is taken by migraine sufferers because it has been found that people who frequently experience headaches and migraines tend to have low blood and brain magnesium levels (1).

University of Maryland recommends taking 300 to 600mg of magnesium per day. One study in premenopausal women has shown that even 200mg of magnesium per day brought about significant relief and decreased frequency of migraine attacks.

Magnesium Dosage for Anxiety

People with anxiety may benefit from magnesium supplements. Magnesium amounts for anxiety range between 400 and 600 mg per day; taken in several divided doses.

Some people report relief from soaking in a hot tub with magnesium sulfate crystals (Epsom salts).  The bath releases magnesium ions, which are then absorbed through the skin. If you choose this approach, put a cup or two of Epson salts in the bath and stay in it for at least 15 minutes.

Magnesium for Depression

People experienced relief from using 125 to 300mg of magnesium several times daily; some of it taken with meals and some close to bedtime to help alleviate any sleep problems associated with depression (2).

The forms most commonly used for depression are magnesium glycinate and taurate since they seem to be the ones that are best absorbed in the brain.

Sleep problems and insomnia

In one study in elderly people (3) 500mg of magnesium daily significantly improved different measures of insomnia (including sleep time, early awakenings, and sleep efficiency). The study has also shown a significant decrease in night time cortisol (stress hormone that keeps you awake) and increase in melatonin (hormone that promotes sleep).

Magnesium also helps improve other conditions that contribute to poor sleep, such as restless leg syndrome, muscle cramps and depression.

Magnesium Dosage for Muscle Cramps in Pregnancy

Taking 100mg of magnesium 3 times daily seem to improve muscle cramps that often come up in pregnancy. 

Generally recommended intake of magnesium for pregnant women is 350mg daily, which can be taken in several doses or in one daily serving – depending on your own personal preferences.

Magnesium for Irregular Heartbeats

Magnesium is sometimes used for preventing irregular heartbeats (episodes of cardiac arrhythmia).  The forms that have been used include magnesium aspartate and magnesium chloride. The doses have been as high as 3 grams per day. You should never take this much magnesium without being supervised by your doctor.

Diabetes (type 1 and 2) and Insulin Resistance

People with diabetes (both type 1 as well as type 2) tend to have lower levels of magnesium than healthy people. Taking supplements with magnesium restores depleted magnesium levels and may help with insulin production and blood sugar control.

Many doctors recommend that people with diabetes and insulin resistance take between 200 and 600mg of magnesium per day.

Magneisum for High Cholesterol Levels

Magnesium supplements have been shown to lower high cholesterol levels and increase the levels of good (HDL) cholesterol). Doses taken for lowering cholesterol range between 300 and 500mg of magnesium per day.

For Osteoporosis

Magnesium plays a key role in bone health. Different dosages have been used for treating osteoporosis; some as high as 1800mg of magnesium (in the form of magnesium hydroxide). This dose has been taken for 6 months and has been followed by a lower maintenance dose of 600mg magnesium daily.

If you decide to take magnesium supplements on your own (without medical supervision), don't go above 400mgs daily.

When and How to Take a Magnesium Supplement

Oral Magnesium

The most popular way of taking magnesium is by mouth in either pill or powder form.  Most people take magnesium once daily or divided evenly into 2 or more servings throughout the day (this is recommend when you are taking larger doses of magnesium). People who take magnesium for sleep problems and insomnia tend to take their whole daily dose about an hour before bedtime.

Some don’t take magnesium regularly, but only on as needed basis. Such is the case with magnesium taken for constipation or as part of heartburn remedy.

When you are starting out with magnesium supplements, first see how you respond to small doses (100 to 200mg of magnesium). Many experts suggest that you then increase your magnesium intake in 100mg increments. This way you will minimize the risk of gastrointestinal upset and associated symptoms (nausea, diarrhea). 

Magnesium is better absorbed when taken on an empty stomach; however, this makes it more likely to cause stomach upset and diarrhea. For that reason many people prefer to take it with food.

Magnesium in nutritional supplements is generally bound to some other substance. The forms that you will typically come across are magnesium oxide, magnesium sulfate, magnesium citrate, and magnesium glycinate, malate, taurate, aspartate, and l-threonate.  There are quite a few differences between these forms and each has its own pros and cons.

Transdermal Magnesium: Magnesium Oil and Epsom Salts

If magnesium is causing you bowel issues, you might want to try taking it in through skin. Transdermal magnesium comes in the form of magnesium oil and Epsom salts.

Magnesium oil is not actually an oil; the name comes from the oily texture that arises once magnesium chloride flakes are mixed with water. Depending on the form of magnesium oil that you have you can either spray it on the skin or apply it directly as massage oil. Gently rub it in and leave it for at least 20 minutes. After that time passes, gently wipe down any residue.  

Epsom salts contain magnesium bound to sulfate crystals. To make a bath with Epsom salts, fill your bathtub with hot water and put in 1 to 2 cups of Epsom salts (for an average size tub; if you have an extra large tub, you need to use more). 

Epsom salt council recommends soaking for at least 12 minutes. You can also add some essential oils to your bath to make it even more enjoyable, such as lavender, which is well known for its relaxing properties.

Safety and Side Effects

Magnesium supplements are generally considered safe when you take them in recommended amounts (350mg for adults).

At higher dosages, magnesium may cause a range of side effects.  Most common side effects include loose stools, nausea and stomach pain.

In extremely high doses, magnesium can be toxic and may lead to low blood pressure, irregular heartbeats, lethargy, confusion, muscle weakness, difficulty breathing and even cardiac arrest.

Who Should be Cautious with Magnesium Supplements

Certain groups of people should not take magnesium supplements or should take them under medical supervision.

People with Kidney Disease or Impaired Kidney Function

If you have kidney problems, your kidneys may not be able to efficiently eliminate magnesium from your body. This can lead to too much magnesium in the blood. Consult with your doctor before using any magnesium supplements.

With Certain Heart Conditions

Supplemental magnesium may make certain heart conditions worse. These include myasthenia gravis, atrial fibrillation and slow heart rate.

People with Bleeding Disorders

Magnesium may slow down blood clotting, which may increase the risk of bleeding if you have a bleeding disorder.

Pregnant and Breastfeeding Women

Magnesium is an essential mineral and your needs for this mineral increase when you are pregnant or breastfeeding.

Current Food and Nutrition Board recommendations are that pregnant women consume 350 mg of magnesium per day and breastfeeding women 320 mg per day.


Children need to get enough magnesium either from the foods they eat or from magnesium supplements. The recommended magnesium intakes for children are lower than for adults. We've discussed the recommended amounts for different age groups at the beginning of this article.  

Interactions with Prescription Medications

Magnesium supplements can affect how certain medications are metabolized in the body.

Antacids (medications for heartburn)

Magnesium is often taken together with other substances that work against stomach acid. When used this way, magnesium enhances the effect of other antacids.

When magnesium is used for constipation, antacids might reduce its laxative effect, so you might need to take a higher dose.


Magnesium interacts with different kinds of antibiotics. It decreases their absorption and makes them less effective. These medications include with aminoglycosides, quinolone antibiotics and tetracycline antibiotics. To prevent this interaction, take antibiotics at a different time than magnesium supplement (2 hour before or at least 4 hours after magnesium supplement).

Bisphosphonates (medications for osteoporosis)

Magnesium interferes with the absorption of medications used for treating osteoporosis. That is why these medications should be taken at least 2 hours before taking magnesium supplement.

Digoxin (medication used for atrial fibrillation and heart failure)

Digoxin may lead to increased excretion of magnesium in urine and can thus lower magnesium levels in the body. If you are on Digoxin, it is important that you take a magnesium supplement since low levels of magnesium can make side effects from digoxin more severe.

Gabapentin (for treating seizures)

Magnesium decreases how much gabapentin is absorbed and may diminish the effectiveness of this medication.

Medications for Diabetes

Magnesium may increase absorption of medications that are used for controlling blood sugar levels. You might need to take lower doses of these medications, so that your blood sugar won't fall too low.

Calcium Channel Blockers (medications for high blood pressure)

Similar to calcium channel blockers magnesium also block calcium from entering the cells.  If you take calcium channel blockers together with magnesium, your blood pressure may drop too low.  

Anticoagulants (medications that slow down blood clotting)

Magnesium is also known to slow down blood clotting. If taken alongside anticoagulants, magnesium might increase the risk of bleeding.

Diuretics (water pills)

Some water pills (potassium sparing diuretics) may cause you to have an excess of magnesium in your body. Other diuretics, know as loop diuretics, work differently and deplete your magnesium levels. That is why it is important that you talk to your doctor if you are taking magnesium supplements and water pills at the same time.

Levothyroxine (medication for underactive thyroid)

Magnesium has been reported to decrease the effectiveness of medications for underactive thyroid. Don't take magnesium supplements if you are on thyroid medication unless specifically instructed by your doctor.

Taking Magnesium with Other Supplements, Herbs and Foods

Magnesium and Calcium

Magnesium and calcium compete for absorption in the body. Take your calcium and magnesium supplement separately, so that there are at least a couple of hours of delay between them.

Magnesium and Milk

Milk contains calcium, potassium and phosphorus, which all interfere with the absorption of magnesium. Don't drink milk for a while before and after taking your magnesium supplements.

Other Magnesium Interactions

Magnesium may also interact with other supplements and herbs. Be extra cautious about any side effects if you are taking magnesium supplements together with:

  • Herbs and supplements that increase the risk of bleeding
  • Substances that lower blood pressure
  • Supplements for lowering blood sugar
  • Phytoestrogens (such as black cohosh, licorice, ginseng, red clover, evening primrose)
  • Herbs that affect thyroid function (including bacopa, bladderwrack, licorice, nettle, flaxseed, lemon balm, echinacea, and others)
  • Supplements taken for osteoporosis (vitamin D, calcium, vitamin K, soy isoflavones, black cohosh, horsetail, etc)

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