How much magnesium glycinate per day?

There is no single right amount of magnesium glycinate, but there are three numbers that tell you whether a dose is sensible: how much magnesium is in the product, how much magnesium adults need in total, and the upper level for magnesium from supplements. The catch is that the biggest number on the label is usually none of them.

The short answer

For adults, the upper level for magnesium from supplements is 350 mg a day, measured as magnesium itself. Magnesium is only about 14% of magnesium glycinate by weight, so 350 mg of magnesium comes from roughly 2,500 mg of the compound.

That upper level is a ceiling, not a target. Food is the main source of magnesium, and a supplement sits on top of whatever you already eat. The directions on the product label, and advice from a doctor or pharmacist if you have a medical condition or take medicines, come first.

Is 500 mg of magnesium too much?

It depends entirely on 500 mg of what.

If a label says 500 mg of magnesium glycinate, that is the weight of the compound. It supplies only about 70 mg of magnesium, well under the upper level. If a dose supplies 500 mg of magnesium itself, that is above the 350 mg upper level for supplements.

The same confusion runs through most dosing questions, because some labels and websites quote the compound and others quote the magnesium. This table converts one to the other for magnesium glycinate.

Magnesium glycinate (compound)	Magnesium supplied (approx.)	Compared with the 350 mg upper level
500 mg	70 mg	Well under
1,000 mg	140 mg	Under
1,500 mg	210 mg	Under
2,000 mg	280 mg	Under
2,500 mg	350 mg	At the upper level
3,500 mg	490 mg	Over

These figures use the roughly 14% magnesium content of pure magnesium bisglycinate. Real products vary, and a buffered product blended with magnesium oxide carries more magnesium per gram. The "equivalent to magnesium" figure on an Australian label is always the more reliable number. Our guides to elemental magnesium and bisglycinate, glycinate and buffered magnesium explain why.

Read the label per dose, not per capsule

Australian labels for mineral supplements show the magnesium equivalent for each capsule, tablet or scoop. The directions then say how many to take. The daily amount is the equivalent figure multiplied by the number of units in a dose, and by the number of doses a day.

A product with 125 mg of magnesium per capsule and directions to take two a day supplies 250 mg of magnesium a day. That is the number to hold against the upper level. Our guide to reading a supplement label walks through the rest of the panel.

How much magnesium adults need in Australia

Australian recommended dietary intakes cover magnesium from all sources, with food as the main one.

Group	Recommended intake (mg a day)
Men 19 to 30	400
Men 31 and over	420
Women 19 to 30	310
Women 31 and over	320
Pregnancy	350 to 400, depending on age
Breastfeeding	310 to 360, depending on age

These are total intakes, not supplement doses. Green leafy vegetables, legumes, nuts, seeds and wholegrains are all good sources. Magnesium from food does not count towards the upper level, because healthy kidneys clear what the body does not need.

Where the 350 mg upper level comes from

The upper level was set in 1997 by the US Institute of Medicine at 350 mg a day for adults, from supplements and medicines only. The limiting effect it was based on was diarrhoea, not toxicity. Magnesium that is not absorbed draws water into the bowel, and that is the first problem to appear as supplement doses rise.

Some researchers think the figure is now too cautious. A 2023 review of trials published since 1997 found that most studies giving single-ingredient magnesium at doses up to 1,200 mg a day reported no significant difference in diarrhoea compared with control groups, and argued the upper level should be re-evaluated. That is a case for review, not a new limit. Until the reference values change, 350 mg is the figure to work with.

What doses the research used

The largest placebo-controlled trial of magnesium bisglycinate to date gave adults reporting poor sleep 250 mg of magnesium a day, as two capsules each containing 893 mg of the compound. A randomised trial comparing an amino acid chelate with magnesium citrate and magnesium oxide used 300 mg of magnesium a day for 60 days.

Both doses sit under the 350 mg upper level. Neither trial was designed to find the right dose for anyone else, so they show what has been studied rather than what you should take. Our review of magnesium glycinate and sleep covers the sleep trial in detail.

Adding it up across products

The upper level applies to all your supplemental magnesium together. Magnesium turns up in multivitamins, sports and electrolyte products, some antacids and some laxatives. Taking a magnesium supplement alongside any of these means adding the equivalent figures from each.

It is also worth checking every label for vitamin B6, which the TGA notes is found in some magnesium products as well as multivitamins. The TGA is tightening controls on higher-dose vitamin B6 products because of the risk of nerve damage.

One dose or two?

The share of magnesium the body absorbs falls as the amount taken at once rises. In one study of healthy adults, the fraction absorbed from a meal fell from 65% to 11% as the magnesium content increased, even though the total absorbed still rose. Splitting a larger daily amount into two smaller doses is one way to work with that. Our guide to magnesium absorption explains the mechanism.

Signs a dose does not suit you

Loose stools, nausea or stomach cramping are the usual signs that more magnesium is reaching the bowel than is being absorbed. Magnesium glycinate has a good record for gut tolerance, but no form is immune at higher doses. Reducing the dose or splitting it usually helps, and stopping is always an option. Our guide to side effects and interactions covers what to look out for.

When to talk to a doctor or pharmacist

Get advice before starting magnesium, rather than after, if any of these apply:

• Reduced kidney function. The kidneys clear excess magnesium, so it can build up when they are not working well.
• Prescription medicines. Magnesium interacts with some antibiotics, osteoporosis medicines and thyroid medicine, and some diuretics and long-term reflux medicines change magnesium levels.
• Pregnancy or breastfeeding. Speak with your doctor, midwife or pharmacist.
• Children. Adult doses are not doses for children.

Nothing on this page is a substitute for individual medical advice. Always read the label and follow the directions for use.