Magnesium: who should take it, when, and which kind

What is magnesium?

Magnesium is an essential mineral (a nutrient your body can't make, so you have to get it from food). It's used in more than 300 chemical reactions in your body.

In simple terms, it's your body's "relax button" and a part in its "energy factory." It helps muscles release, calms your nerves and helps turn food into energy.

The problem is that it's one of the minerals people today are most likely to run low on. We eat a lot of processed food, and coffee, alcohol and stress cause us to lose more of it.

Magnesium benefits: where it may help

• Sleep and stress: It's needed to make calming brain chemicals (GABA and serotonin). It's popular with people who are tired but can't fall asleep.
• Muscle knots and cramps: It helps muscles contract and then relax. Many people with frequent leg cramps say they had far fewer after about 4 weeks.
• Fatigue: Together with B vitamins, it helps turn food into energy.
• Eyelid twitches and numbness in hands and feet: These are signs of irritable nerves and muscles, and they often show up when magnesium is low.
• Menstrual cramps: It may help ease cramps by relaxing excess contractions of the uterine muscles.
• Blood pressure and blood sugar: It helps relax blood vessels and helps insulin (the hormone that lowers blood sugar) work well.
• Constipation: Magnesium oxide draws water into the gut to soften stool.

Magnesium deficiency checklist

If 3 or more of these apply, magnesium is worth trying.

• □ The skin under your eye or on your face twitches
• □ You often get leg cramps, or your hands and feet go numb
• □ You're tired, but when you lie down you can't fall asleep
• □ You feel anxious and your heart races for no reason
• □ Your muscles feel stiff and you have no energy even after sleeping
• □ Your nails break easily and you're losing a lot of hair
• □ Your head feels foggy and it's hard to focus
• □ You have bad menstrual cramps

You're even more likely to run low if:

• You drink several cups of coffee a day or drink alcohol often (you lose it through urine)
• Your work is mentally demanding and stressful
• You eat mostly bread, noodles and processed foods
• You have low stomach acid or a weak stomach
• You've taken medication for a long time for a chronic condition like diabetes

Also note that most of your magnesium is stored in bones and muscles. So you can be low even if a standard blood test comes back normal.

Talk to your doctor first if…

Your kidneys flush out extra magnesium on their own, so it's fairly safe for healthy people. But talk to your doctor first if any of these apply.

• Your kidneys aren't healthy: Magnesium may not clear and can build up. Even normal doses can be a problem.
• You have heart disease: Be sure to check if you have a serious arrhythmia, just had heart attack surgery, or are having your medication adjusted.
• Your blood pressure is naturally very low: Magnesium can lower blood pressure a bit more. If you want to take it, start very small, like 50–100 mg.
• Babies 2 and under, and older adults on many medications
• You have a bowel condition with frequent diarrhea: diarrhea-type IBS, ulcerative colitis, Crohn's disease, etc.

Types of magnesium compared: glycinate, citrate, oxide

Magnesium doesn't come alone — it's bound to another substance. What it's bound to changes absorption, how it sits in your stomach, and the price. On the label, the ○○○ in "Magnesium ○○○" is that name.

You'll often hear that magnesium oxide is "the worst absorbed." But some studies show its absorption isn't very different from other forms. As long as your stomach handles it, it's not automatically a bad choice.

Don't give up on magnesium entirely just because one form didn't agree with you. Different forms suit different people, and simply switching forms often solves the problem.

When to take magnesium and how much

Bottom line: 200–400 mg a day, after meals. If sleep is your goal, after dinner is best.

Remember how to take it in this order.

1. Always take it after meals. Magnesium needs stomach acid and food to dissolve and absorb well. On an empty stomach, absorption drops and you're more likely to get a stomachache or diarrhea.
2. After dinner if sleep is your goal; otherwise, after breakfast or lunch is fine too.
3. Split it if you take 2 or more capsules a day. Dividing it between morning and evening helps absorption and is easier on your stomach.
4. Start small. Try 1 capsule for about a week, and increase if you're doing fine.

Give it at least 4 weeks, and up to 6 months or more, of steady use. One approach is 400 mg for the first 6 months, then dropping to 200 mg for maintenance. Many say there's no need to cycle off it regularly.

How to choose magnesium: 3 things to check on the label

1. Which form it is — Check the name: glycinate, citrate, oxide, etc. Use the table above to see if it fits your goal.
2. How many mg of elemental magnesium per capsule — In the Supplement Facts, check the number next to "Magnesium (as ○○○)." For example, even a 1,000 mg taurate capsule contains only 100 mg of actual magnesium.
3. How many capsules a day, and so how much it really costs — Better forms tend to have less per capsule, so you need 2–4 capsules a day.

Be skeptical of these products:

• Products that claim a blend of forms but give no ratio, with 400–500 mg per capsule: Magnesium oxide is usually the main ingredient. Better forms are bulky, so you can't fit that much in one capsule.
• Products with "glycinate" in big letters but magnesium oxide in the ingredient list: These may be cheap blends.

Magnesium side effects: why it causes diarrhea and what to do

The most common side effects are stomach pain, heartburn, gas and diarrhea. That's because magnesium draws water into the gut. People with low stomach acid get them more often.

If it bothers you, try these steps in order.

1. Take it right after a meal
2. Split your daily amount
3. Lower the dose
4. Switch forms: oxide → citrate or malate → glycinate

If the diarrhea keeps coming back anyway, don't push through — stop.

Glycinate can rarely cause allergic reactions like hives or itching. If that happens, switch to another form like citrate.

It's very rare, but stop right away if you notice these symptoms. Take 1–2 weeks off, get checked by a doctor, and then switch to a different product.

• Double vision
• Dizziness and a sudden drop in blood pressure
• Shallow breathing or a slow pulse

Stacking several calming supplements (theanine, GABA, melatonin, ashwagandha, etc.) can make you dizzy. If you feel drained in the morning, try lowering the dose.

Can you take magnesium and calcium together?

It's best to take them at different times. Many say they interfere with each other's absorption when taken together. For example, calcium in the morning and magnesium in the evening. If possible, space it apart from the minerals in your multivitamin too.

Some people take a combo with calcium, magnesium and vitamin D in one capsule. But if you have clear signs of low magnesium, getting enough magnesium on its own comes first.

Common good pairings: B vitamins and CoQ10 for fatigue; lecithin and melatonin for sleep; theanine, ashwagandha and rhodiola for stress; and vitamin D and K2 for bone health.

Combinations

Works well with: B vitamins (B complex), Coenzyme Q10 (CoQ10), Vitamin D, Vitamin K2, Lecithin, Melatonin, L-Theanine, Ashwagandha, Rhodiola

Space apart from: Calcium

Frequently asked questions

Related concerns