How much magnesium do you need a day?

Find out the recommended daily magnesium intake in Australia by age and life stage, the best food sources, how much is too much, and when a supplement may help.

Around three in ten Australians did not get enough magnesium from food and drink in 2023, according to the most recent Australian Bureau of Statistics figures. Magnesium is one of the minerals people ask about most, and the honest answer to "how much do I need?" depends on your age, sex and life stage.

This article outlines the recommended daily magnesium intakes for Australia, how these needs change throughout life, where the mineral is found in food, how much is too much, and what to consider if you are considering a supplement.

Why magnesium matters in the body

Magnesium is an essential mineral, which means the body cannot make it and has to get it from food. It is involved in more than 300 enzyme systems, according to the National Institutes of Health Office of Dietary Supplements, including processes that affect muscle and nerve function, energy production and protein synthesis.

The Australian Bureau of Statistics describes magnesium as necessary for protein production, muscle and nerve function, blood glucose control and bone development. Healthdirect similarly notes that magnesium plays a role in healthy muscles, nerves, bones and blood sugar levels. The NIH Office of Dietary Supplements notes that an adult body holds about 25 grams of magnesium, with 50 to 60% stored in the bones and most of the rest in soft tissue such as muscle.

How much magnesium do you actually need?

In Australia, the Recommended Dietary Intake (RDI) for magnesium is 400 to 420 mg a day for adult men and 310 to 320 mg a day for adult women. The RDI is the amount estimated to meet the needs of nearly all (97 to 98%) healthy people in a given age and sex group.

These figures refer to total magnesium from all sources: food, drinks and any supplement combined. Because the body holds a reserve and the kidneys regulate what is kept or excreted, day-to-day variation matters less than your typical intake over weeks.

How magnesium needs change across life stages

Requirements rise through childhood and adolescence, then differ between men and women in adulthood.

Recommended intakes by age and sex

The NHMRC sets the following Recommended Dietary Intakes:

Where Australians most often fall short

The latest ABS figures, published in 2026, show where intakes most often fall short in practice. In 2023, adults were more likely than children to have an inadequate magnesium intake (35.9% compared with 13.5%), and the proportion was higher in men than women overall (35.2% compared with 27.3%). Men aged 75 and over (50.2%) and adolescent girls aged 12 to 17 (43.9%) were the groups least likely to meet their requirements.

Signs your magnesium intake may be falling short

Magnesium deficiency is uncommon in otherwise healthy people, because the kidneys limit how much is lost in urine. When intake is low over a long period, Healthdirect lists possible early signs such as loss of appetite, nausea, fatigue and weakness, with muscle cramps and spasms appearing as a deficiency becomes more pronounced.

These signs are general and overlap with many everyday causes, so they are not a diagnosis. A blood or urine test ordered by a doctor is the way to check magnesium status. People more likely to run low include older adults, those who eat very little, and people with certain medical conditions or medications that affect how the body handles magnesium. If you are experiencing persistent symptoms, it is worth speaking with your GP.

Where magnesium comes from in food

Most people can meet their magnesium needs through everyday eating, without a supplement. The mineral is found across a wide range of whole foods, and the body can absorb a greater proportion of it when dietary magnesium is low. The sources below are the most reliable places to find it.

Best food sources

Foods rich in magnesium include leafy green vegetables, legumes, nuts, seeds and wholegrains, according to Healthdirect. Magnesium sits at the centre of the chlorophyll molecule, which is why green plants are reliable sources. Practical, magnesium-dense additions to a day's eating include:

• A handful of almonds, cashews or pumpkin seeds
• Cooked legumes such as lentils, chickpeas or black beans
• Wholegrains like brown rice, oats and wholemeal bread
• Leafy greens such as spinach and silverbeet
• Dark chocolate and bananas in smaller amounts

Everyday sources that add up

Some sources contribute more than people expect. ABS data identifies cereal-based mixed dishes, water, coffee and ready-to-eat breakfast cereals among the leading contributors to magnesium intake across the Australian diet, with drinking water alone supplying close to one tenth of the total, based on Australian intake data.

Can you have too much magnesium?

For people with healthy kidney function, this is very unlikely from diet alone. Healthdirect explains that excess magnesium from food is cleared by the kidneys through urine, so a balanced diet will not cause an overload in people with healthy kidneys.

Supplements are different. The NHMRC sets an Upper Level of Intake of 350 mg a day for magnesium from supplements, separate from the magnesium you get in food. Diarrhoea is the first sign of taking too much from supplements, which can also cause nausea and abdominal cramping. Staying within label directions keeps intake within this guidance for most healthy adults.

Supplementation considerations

A supplement is one option when dietary magnesium may be falling short, for example in older adults or people whose diets are low in wholegrains, legumes and leafy greens. It sits alongside a varied diet rather than replacing it.

Choosing a magnesium form

Magnesium comes in several forms, and they differ in how the mineral is bound. Magnesium glycinate is magnesium combined with the amino acid glycine, a form often chosen because it tends to be gentle on the digestive system. When comparing products, check the elemental magnesium figure on the label rather than the total compound weight, since this is the amount that counts toward your daily intake.

What Blackmores Magnesium Glycinate contains

Blackmores Magnesium Glycinate is formulated with 150 mg of elemental magnesium per tablet (as magnesium glycinate), with no added artificial flavours, colours or sweeteners, and it contains sulfites. It is a one-a-day tablet for general health, taken with food, with a maximum of two tablets in 24 hours.

In terms of what magnesium does in the body, the formula is designed to support muscle health, muscle function and nervous system function, and to contribute to a healthy stress response, healthy sleeping patterns, energy levels and electrolyte balance. It may also help relieve muscle cramps and mild muscle spasms when dietary intake is inadequate. You can compare options across the Blackmores magnesium range, which includes tablets and powders. Vitamins and minerals can only be of assistance if dietary intake is inadequate.

Building a balanced magnesium routine

Meeting your magnesium needs is mostly about consistency rather than any single change. A practical approach:

• Build meals around plants, aiming for a mix of vegetables, wholegrains, legumes, nuts and seeds across the week
• Keep some easy sources on hand, such as a jar of mixed nuts or tinned legumes
• If you take a supplement, take it with food and at a time you will remember, since steady daily intake matters more than dose size
• Check the elemental magnesium figure on any supplement label, not just the total compound weight, and keep supplemental magnesium within the 350 mg daily upper level unless advised otherwise by a health professional

When to see a healthcare professional

Most magnesium questions are answered by diet and lifestyle, but some situations call for professional input. Speak with your GP, pharmacist or an accredited practising dietitian if you have persistent symptoms such as ongoing fatigue, muscle cramps or twitching, if you have a condition or take a medication that affects magnesium levels, if you have reduced kidney function (which changes how magnesium is cleared), or if you are pregnant or breastfeeding and unsure about your intake. A simple blood or urine test can clarify whether magnesium is actually the issue.

Key takeaways

Magnesium needs change across life, rising through childhood and adolescence before settling at higher levels for men than women in adulthood. Around 31% of Australians did not meet their magnesium needs from food in 2023, a figure that has eased slightly over the past decade but remains highest in older men and teenage girls. Leafy greens, legumes, nuts, seeds and wholegrains are dependable food sources, and most people can meet their needs through diet. You cannot get too much magnesium from food, but supplemental magnesium has a 350 mg daily upper level. Where diet falls short, a supplement such as magnesium glycinate is one option to sit alongside balanced eating.

Frequently asked questions

How much magnesium do I need per day in Australia?

The NHMRC Recommended Dietary Intake is 400 to 420 mg a day for adult men and 310 to 320 mg a day for adult women. Needs are lower for children and slightly higher in pregnancy. This total covers magnesium from food, drinks and supplements combined.

Can you take too much magnesium?

Not from food, as healthy kidneys clear any excess. From supplements, the upper level is 350 mg a day for adults. Higher supplemental doses can cause diarrhoea, nausea and cramping, so staying within label directions is sensible.

What are the signs of low magnesium?

Healthdirect lists possible early signs of low magnesium as loss of appetite, nausea, fatigue and weakness, with muscle cramps appearing as a deficiency becomes more pronounced. These are general and not a diagnosis. A doctor can confirm magnesium status with a blood or urine test.

Can you take magnesium every day?

Yes. Magnesium supplements are designed for daily use, and consistent intake helps maintain steady levels. Take them with food, follow the label, and keep supplemental magnesium within the 350 mg daily upper level unless your health professional advises otherwise.

Which foods are highest in magnesium?

Leafy green vegetables, legumes, nuts, seeds and wholegrains are among the richest sources. Drinking water also contributes a meaningful share of magnesium across the Australian diet.

Always read the label and follow the directions for use.
Disclaimer: This article provides general information only and is not intended to diagnose, treat, cure, or prevent any disease. The information presented is not a substitute for professional medical advice. If you have concerns about your health, please consult your GP or healthcare provider for a personalised assessment and recommendations. Supplements should not replace a balanced diet.