Written by the Priceline Pharmacy Pacific Fair team. Reviewed by Jason Markey, BPharmSci, MPharm, Owner and Pharmacist.
General health information from a registered pharmacist. It doesn’t replace advice from your own pharmacist or doctor.
Most people get all the magnesium they need from food, and healthdirect notes that magnesium deficiency isn’t common in healthy adults. If you do take a supplement, the type matters: magnesium citrate, chloride, lactate and aspartate are absorbed better than magnesium oxide. And the evidence for two of the most common reasons people buy magnesium, leg cramps and sleep, is weaker than many people expect.
If you’ve stood in front of the vitamin shelves at Pacific Fair comparing a dozen magnesium products, this guide covers what each type means, who may need extra magnesium, and the medicines it shouldn’t be taken with at the same time.
Which type of magnesium is best absorbed?
Magnesium in supplements comes bound to another compound, and that affects how much your body can use. The US National Institutes of Health (NIH) fact sheet on magnesium says:
- Citrate, chloride, lactate and aspartate tend to be better absorbed. Forms that dissolve well in liquid are generally absorbed more completely.
- Oxide and sulfate are absorbed less well.
- Glycinate (or bisglycinate) and other “amino acid chelate” forms are also widely sold. They’re often described as gentle on the stomach, but the independent sources we checked don’t compare them directly with the forms above.
Two label tips: look for how much magnesium itself each tablet or scoop provides, not just the weight of the compound, and check whether the product contains other ingredients such as vitamin B6 (more on that below).
Does magnesium help with leg cramps or sleep?
This is where it pays to look at the research rather than the marketing.
Leg cramps: a Cochrane review, which pools the results of randomised trials, found it is unlikely that magnesium supplements give older adults any meaningful protection from muscle cramps, based on moderate-certainty evidence. For cramps in pregnancy, the results were conflicting and the reviewers were very uncertain whether magnesium helps. Muscle spasms can be a sign of severe magnesium deficiency, though, so if you’re low, correcting that matters.
Sleep: magnesium is often marketed for sleep and relaxation, but it isn’t an established treatment for insomnia. healthdirect’s magnesium pages don’t list sleep among its roles, and its insomnia advice starts with sleep habits, such as reducing alcohol and limiting caffeine to mornings. Our trouble sleeping tips cover those habits in more detail. If you’d like to try magnesium anyway, check it with a pharmacist first, and keep working on the habits at the same time.
Who might be low in magnesium?
healthdirect says deficiency is rare in healthy people. You’re more likely to be low if you:
- are older
- have type 2 diabetes
- have a digestive condition such as Crohn’s disease, or long-term vomiting or diarrhoea
- have kidney problems
- have alcohol dependence
- take some medicines long term, including fluid tablets (diuretics) and reflux medicines called proton pump inhibitors. The NIH notes these reflux medicines can cause low magnesium when taken for a long time, typically more than a year.
healthdirect lists signs of low magnesium as poor appetite, nausea and vomiting, tiredness and weakness. Severe deficiency can cause muscle spasms and abnormal heart rhythms. It’s diagnosed with a blood or urine test, so see your GP rather than guessing.
How much do you need? healthdirect gives a recommended daily intake of 400 mg for men aged 19 to 30 and 420 mg for men 31 and over, and 310 mg for women aged 19 to 30 and 320 mg for women 31 and over. Needs are a little higher in pregnancy. The NIH fact sheet gives an upper limit of 350 mg a day of magnesium from supplements and medicines for adults. That limit doesn’t include magnesium from food.
Can you get enough magnesium from food?
Most people can. Green leafy vegetables, legumes, nuts and seeds, wholegrains, seafood and meat all contribute. healthdirect gives these examples:
| Food | Magnesium |
|---|---|
| Pumpkin seeds (pepitas), 30 g | 159 mg |
| Chia seeds, 30 g | 114 mg |
| Almonds, 30 g | 80 mg |
| Cashews, 30 g | 75 mg |
| Brown rice, ½ cup cooked | 72 mg |
| Spinach, ½ cup boiled | 57 mg |
| Salmon, 100 g cooked | 30 mg |
A handful of nuts and seeds on your breakfast or in a beach bag goes a long way.
What are the side effects, and which medicines should you space it from?
Side effects: diarrhoea is the most common, along with nausea and tummy cramps. Taking far more than the recommended amount can lead to an irregular heartbeat or even cardiac arrest, according to healthdirect.
Vitamin B6: some magnesium products also contain vitamin B6. healthdirect advises stopping and seeing your doctor if you notice tingling, burning or numbness.
Kidney disease: healthy kidneys clear extra magnesium through your urine. The NIH notes the risk of magnesium toxicity rises when kidney function is reduced, so check with your doctor before taking magnesium if you have kidney disease.
Medicine timing: magnesium can bind to some medicines in the gut so less is absorbed. The NIH advises:
- some antibiotics (the tetracycline and quinolone groups): take the antibiotic at least 2 hours before, or 4 to 6 hours after, a magnesium supplement
- some osteoporosis medicines (bisphosphonates): separate them from magnesium by at least 2 hours
If you take thyroid medicine or any other regular medicine, ask your pharmacist how to time a magnesium supplement around it. Don’t change how you take a prescribed medicine without advice. For other common combinations to watch, see supplements that can interact with your medicines.
How our pharmacists can help
Our pharmacists can help you choose a form and dose, check magnesium against your other medicines, and work out a timetable if you take antibiotics, osteoporosis or thyroid medicines. We stock everyday and practitioner-range supplements, and you can read more about our vitamins and supplements advice. You can also compare products in the cramp and muscle range on priceline.com.au and ask us in store before you buy.
When to see a pharmacist or GP
See a GP, such as our in-store Help Medical GPs, if:
- you have frequent or painful cramps, or they disturb your sleep
- you’ve been tired, weak or off your food for a while
- you have kidney disease, type 2 diabetes or a bowel condition and are thinking about a supplement
- you’ve taken reflux medicines or fluid tablets for a long time and wonder whether your magnesium should be checked
- you notice tingling, burning or numbness while taking a supplement
- diarrhoea from a supplement doesn’t settle when you stop it
Ask a pharmacist before taking magnesium if you’re pregnant or breastfeeding, or if you take any regular medicines. If you think someone has taken too much, call the Poisons Information Centre on 13 11 26.
Call 000 in an emergency. If someone has chest pain, a very irregular heartbeat or collapses, call triple zero (000).
Sources
This article is general information only and isn’t a substitute for personal advice from your doctor or pharmacist. Always read the label and follow the directions for use. If symptoms persist or you’re worried, talk to your pharmacist or GP. In an emergency, call 000.
Talk to our pharmacists at Pacific Fair
Pop in, no appointment needed. We’re on the ground floor of Pacific Fair Shopping Centre, Broadbeach, open 7 days and until 9pm on Thursdays.