Nutrition
Magnesium: how much, what form, and when
Magnesium is the supplement people ask me about most, usually because they read something about sleep. Here is what the reference numbers actually say, what the evidence supports, and what it does not.
How much magnesium Canadian adults are told to get
These are Health Canada’s Recommended Dietary Allowances, which is the intake judged sufficient for most healthy people. They count everything you eat and drink, not just what is in a capsule.
| Age | Men | Women |
|---|---|---|
| 19 to 30 | 400 mg | 310 mg |
| 31 to 50 | 420 mg | 320 mg |
| 51 to 70 | 420 mg | 320 mg |
Pregnancy and breastfeeding have their own values, and they are not the same as the figures above. If either applies to you, look them up in the Health Canada table linked at the bottom of this page rather than working from a general number.
The 350 mg number almost everyone misreads
Health Canada sets a Tolerable Upper Intake Level of 350 mg per day of magnesium for adults. People see that, compare it to the 420 mg recommendation above, and conclude the two contradict each other.
They do not. The 350 mg ceiling applies only to supplemental magnesium: tablets, powders, the magnesium added to a multivitamin. Magnesium you get from food is not counted against it, because the kidneys handle dietary magnesium in a way they do not handle a large single supplemental dose.
So the practical reading is: aim for the recommended total from food first, and keep what you add on top of that from a bottle under 350 mg a day unless a healthcare provider has told you otherwise.
Why the form on the label matters
Magnesium is never sold as the bare mineral. It is bound to something, and that something changes how much elemental magnesium is in the tablet and how it behaves in the gut. Two products can both say "magnesium" and differ substantially.
- Check the elemental magnesium figure, not the compound weight. A 500 mg magnesium oxide tablet does not deliver 500 mg of magnesium.
- Magnesium is one of the more common causes of loose stools among mineral supplements, and the forms differ in how likely that is. If one form disagrees with you, another may not.
- Sustained-release formats spread the dose out rather than delivering it all at once, which some people tolerate better.
When to take it, and what it can interfere with
There is no strong evidence for one correct time of day. Consistency matters more than timing, and splitting the daily amount across two smaller doses is a reasonable approach if a single dose bothers your stomach.
Timing does matter for interactions. The US National Institutes of Health notes that magnesium can interact with oral bisphosphonates, tetracycline and quinolone antibiotics, and that some medications affect magnesium levels in turn. If you take prescription medication, this is a question for your pharmacist, and it is a quick one to ask.
About the sleep question
I am not going to tell you magnesium fixes sleep. I sell supplements and that claim would be worth money to me, which is exactly why you should be suspicious of anyone who makes it casually.
What is true: magnesium is involved in a very large number of processes in the body, low intake is common, and correcting a genuine shortfall is worth doing on its own merits. What is not established: that taking magnesium reliably improves sleep in people who are not short of it. Health Canada licenses natural health products for specific claims, and a general sleep claim is not among those granted to magnesium supplements.
If you want to try it anyway, that is a reasonable thing to do within the limits above. Just go in knowing what the evidence does and does not carry.
The magnesium products I carry
Three options, and they are genuinely different from each other. If you are not sure which fits, ask me rather than guessing from the labels.
Cal-Mag Plus
A chewable calcium and magnesium tablet with vitamin D, for people who would rather not swallow a horse-pill mineral.
This page is general information, not medical advice. Talk to your healthcare provider before starting any new supplement, especially if you are pregnant, nursing, or taking medication.
Questions people actually ask
How much magnesium should I take in a day?
Health Canada’s recommended total intake is 400 to 420 mg a day for men and 310 to 320 mg a day for women, depending on age, counting food and supplements together. Supplemental magnesium on its own has a separate upper limit of 350 mg a day for adults. Talk to your healthcare provider before starting, particularly if you take prescription medication.
What is the best time of day to take magnesium?
There is no strong evidence for a single best time. Taking it consistently matters more than taking it at a particular hour. If a full dose upsets your stomach, splitting it into two smaller doses often helps. Keep it separate from certain antibiotics and bisphosphonates, and ask your pharmacist about timing if you take prescription medication.
Does magnesium help you sleep?
The evidence is limited and Health Canada does not license magnesium supplements for a sleep claim. Magnesium is worth getting enough of for its own reasons, but I would not sell it to you as a sleep remedy, and if sleep is your main concern your doctor is a better first call than a supplement.
Can I take magnesium with calcium?
Yes, and they are commonly formulated together, which is what Chewable Cal Mag Plus is. Whether you need both depends on what your diet already provides. Talk to your healthcare provider, especially if you already take a calcium supplement for bone health.
Is the price the same as buying from Shaklee directly?
Yes. Shaklee sets one price across Canada, so ordering through my storefront costs exactly the same. It credits me as your ambassador and means you have someone to ask.
Still deciding? Ask me directly.
I would rather answer a real question than have you guess from a web page. Call, email, or send a note and you get me, not a call centre.