The three most common magnesium supplements sold in Canada differ mainly in how much magnesium they deliver and how they affect your gut. Magnesium glycinate is gentle and often chosen for sleep and stress support, magnesium citrate is well absorbed and can loosen stool, and magnesium oxide has the most magnesium per tablet but the body absorbs little of it, so it is mostly used as a short-term laxative.
Picking the right form matters more than picking the highest dose. Below is a practical breakdown of what each form does, who tends to choose it, and how to read the label so you know what you are actually getting.
The short comparison
Magnesium supplements are magnesium bound to another compound, and that compound changes how the mineral behaves in your body. The amount of actual magnesium in each pill, called elemental magnesium, also varies a lot between forms, so two products with the same tablet size can deliver very different doses.
| Form | Elemental magnesium | Gut tolerance | Typically used for |
|---|---|---|---|
| Glycinate | Moderate | Gentle, low laxative effect | Sleep and stress support, general top-up |
| Citrate | Moderate to high | Can loosen stool at higher doses | General magnesium intake, occasional constipation |
| Oxide | High on paper, poorly absorbed | Strong laxative effect | Short-term constipation relief |
Magnesium glycinate: the gentle, sleep-friendly choice
Magnesium glycinate is magnesium bound to glycine, an amino acid. This combination tends to be easier on the stomach and less likely to cause loose stool than other forms, which is why it is a common pick for people who want magnesium in the evening without gut upset.
Magnesium itself is needed for normal muscle and nerve function and plays a role in relaxation, which is why it often comes up alongside other sleep and stress supplements. We go into more depth on how magnesium fits alongside other options like melatonin and L-theanine in our practical guide to supplements for sleep and stress.
Magnesium citrate: well absorbed, moderate laxative effect
Magnesium citrate is magnesium combined with citric acid. Research suggests citrate forms are absorbed reasonably well, making this a solid general-purpose choice for people who simply want to close a gap in their magnesium intake.
At higher doses, citrate draws water into the intestines and can have a mild to moderate laxative effect. Some people notice this side effect at the upper end of typical supplement doses, while others tolerate it well. Starting with a lower amount and adjusting based on how your gut responds is a reasonable approach.
Magnesium oxide: cheap, high on paper, poorly absorbed
Magnesium oxide has a high percentage of elemental magnesium by weight, which sounds appealing on a label, but the body absorbs only a small fraction of it. Most of what you take passes through the digestive tract, pulling water with it.
This is exactly why magnesium oxide is the base ingredient in many over-the-counter laxative products. If your goal is steady magnesium intake for muscle, nerve, or sleep support rather than a bowel-clearing effect, oxide is usually not the most efficient choice.
How much magnesium do you actually need
Health Canada's reference intakes set adult targets at 400 mg per day for men aged 19 to 30 and 420 mg for men 31 and older, and 310 mg for women 19 to 30 and 320 mg for women 31 and older. These totals include magnesium from food, and most Canadians get a meaningful portion of their intake from diet already.
For supplements specifically, there is a tolerable upper intake level of 350 mg of magnesium per day from supplement sources alone, separate from food. This limit exists because supplemental magnesium, unlike the magnesium naturally found in food, is more likely to cause diarrhea and stomach upset at high doses. Check the supplement facts panel for the elemental magnesium amount per serving, not just the total weight of the compound, so you can see how it fits against this 350 mg supplement limit.
What to check on the label
Every legitimate natural health product sold in Canada, including magnesium supplements, should carry a Natural Product Number, or NPN, on the label. This means Health Canada has reviewed the product for safety and label accuracy, and you can look it up in the Licensed Natural Health Products Database if you want to confirm the details.
- The specific form used, such as glycinate, citrate, bisglycinate, or oxide
- The elemental magnesium amount per serving, in milligrams
- An NPN, which confirms Health Canada review
- Directions for use and any cautions about combining with other supplements or medications
Who should ask a pharmacist first
People with kidney disease should speak with a doctor or pharmacist before starting magnesium, since the kidneys are responsible for clearing excess magnesium and reduced kidney function changes how the mineral is handled. Magnesium supplements can also interact with certain antibiotics and other medications by reducing absorption, so spacing doses apart or checking with a pharmacist is a sensible precaution.
If you are pregnant, breastfeeding, or considering magnesium for a child, check with a healthcare provider first. And if you are building an evening routine around magnesium and other calming ingredients, our guide on where supplements fit in a wind-down routine covers timing and realistic expectations.
The short version
- Magnesium glycinate is generally the gentlest option and a common choice for evening or stress-related use.
- Magnesium citrate is well absorbed but can loosen stool at higher doses.
- Magnesium oxide has the least reliable absorption and is mainly useful as a short-term laxative.
- Look at elemental magnesium per serving, not just the compound weight, and stay mindful of the 350 mg supplement upper limit.
- Confirm an NPN on the label and ask a pharmacist if you take medications or have kidney concerns.
Shop the products
Frequently asked questions
Which magnesium form is best for sleep?
Magnesium glycinate is the form most often chosen for evening use because it tends to be gentler on the stomach than citrate or oxide. Magnesium is only one piece of a wind-down routine, so results vary and it works best alongside good sleep habits.
Why does magnesium oxide cause diarrhea?
The body absorbs only a small portion of magnesium oxide, so most of it stays in the digestive tract and draws in water, which speeds up bowel movements. This is why oxide is the base ingredient in many laxative products rather than general magnesium supplements.
Can I take more magnesium if I am deficient?
Food sources of magnesium do not carry the same upper limit concerns as supplements, but supplemental magnesium has a 350 mg per day upper limit because higher doses raise the risk of diarrhea and cramping. If you suspect a true deficiency, talk to a doctor rather than self-treating with high doses.
Is magnesium citrate safe to take every day?
Many people take magnesium citrate daily without issue, though some notice looser stool at higher doses. Starting on the lower end and adjusting based on your tolerance is a practical approach.
Does the form of magnesium affect how well it works for muscle cramps?
Magnesium is needed for normal muscle function regardless of the form, but forms with better absorption, like glycinate or citrate, are generally preferred over oxide for consistent daily intake. If cramps persist, it is worth discussing with a pharmacist or doctor, since other causes are common.
Keep reading
- Supplements for Sleep and Stress: A Practical Guide
- Melatonin: How Much, How Early, and What It Won't Fix
- Ashwagandha, L-Theanine and GABA: What the Evidence Says
- Where Supplements Fit in Your Wind-Down Routine
Sources
- NIH Office of Dietary Supplements: Magnesium
- Health Canada: Reference values for elements (minerals)
- Health Canada: Licensed Natural Health Products Database
This article is for general information only and is not medical advice. Talk to your doctor or pharmacist before starting a supplement, especially if you are pregnant or breastfeeding, take medication, or have a health condition.