Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult your GP or a registered health professional before starting any new supplement.
Magnesium is one of the most talked-about supplements on the shelf, and one of the most oversold. You will see it promised for sleep, muscle tension, headaches and mental clarity, usually with the implication that anyone who starts taking it will feel the difference within a fortnight. The honest position is narrower. Magnesium is genuinely essential, some people do not get enough of it from food, and correcting a real shortfall is worthwhile — but a supplement is not a guaranteed treatment for any of those symptoms, and the evidence behind the marketing is thinner than the marketing suggests.
What is well established is that magnesium is a cofactor in more than 300 enzyme systems in the body. This guide covers the magnesium supplements available in New Zealand, how the forms genuinely differ from one another, and the dosing and safety points that the labels tend to skip.
The Form of Magnesium Matters More Than the Brand
This is the single most important thing to understand before buying a magnesium supplement. The form of magnesium determines how well it absorbs and what it is actually good for. Here is the honest breakdown:
- Magnesium glycinate (bisglycinate): Bound to glycine, an amino acid. Better absorbed than oxide and generally the gentlest on the stomach, which is why it suits daily and evening use. There is very little head-to-head human research comparing it directly against the other organic forms, so treat any claim that it is the best-absorbed form — including the ones on the packaging — as unproven. What you reliably pay extra for here is digestive tolerance, not a dramatic absorption advantage.
- Magnesium citrate: Bound to citric acid. Good absorption, affordable, and a mild laxative effect at higher doses — which makes it useful for constipation but less ideal for sleep-focused supplementation.
- Magnesium oxide: The cheapest and most commonly used form in supermarket supplements. Poorly absorbed — the most widely cited measurement put fractional absorption at around 4% (Firoz and Graber, Magnesium Research, 2001), though that was a small study of 16 people and the figure gets quoted with more precision than it deserves. Reasonable if you specifically want the laxative effect; a poor choice if you do not.
- Magnesium malate: Bound to malic acid. Another well-absorbed organic form, often marketed for energy and muscle recovery, though that particular positioning rests on the properties of malic acid rather than on trials of the supplement itself.
- Magnesium threonate: Newer form, claimed to cross the blood-brain barrier more effectively. More expensive, limited but promising research for cognitive function.
Before You Choose: Dose and Safety Basics
Two things are worth settling before you look at any product. The first is dose. The upper limit for magnesium from supplements and medicines is 350mg a day for adults, counted separately from the magnesium in food. Several products sold in New Zealand, including one in the list below, exceed that in a single capsule — so the dose on the label is something to read, not assume.
The second is that magnesium is not inert. It reduces absorption of oral bisphosphonates, and of tetracycline and quinolone antibiotics, so those need to be spaced apart from your magnesium — at least two hours for bisphosphonates, and two hours before or four to six hours after those antibiotics. The risk of magnesium accumulating to harmful levels also rises when kidney function is impaired. If you have kidney disease, take regular medicines, are pregnant, or are supplementing for a persistent symptom, get personal advice before starting rather than after. The dosing section further down goes into more detail.
The Best Magnesium Supplements Available in NZ (2026)
1. Clinicians Magnesium 625 — Best Overall
Clinicians, the NZ supplement brand founded in 1997 by two New Zealand pharmacists, makes one of the more clearly labelled magnesium products available locally. Each capsule of Clinicians Magnesium 625 delivers 125mg of elemental magnesium from a magnesium aspartate complex. It is worth being explicit about what that is: aspartate, not glycinate. That is not a mark against it — the same 2001 study that measured magnesium oxide at roughly 4% found aspartate absorbed about as well as magnesium chloride and lactate — but if it is specifically glycinate you have come looking for, this is not that product. The elemental dose is stated plainly on the panel, which is more than several competitors manage, and 125mg a capsule is a sensible everyday amount. Available from Healthpost.co.nz and most NZ health stores at around NZ$26 for 90 capsules.
Best for: A well-absorbed, honestly labelled everyday magnesium at a moderate elemental dose.
2. GO Healthy GO Magnesium — Widely Available, But Check the Dose
GO Healthy’s magnesium range includes several forms, including their high-strength options. Their GO Magnesium 1-A-Day 500mg delivers 500mg of elemental magnesium from a marine magnesium source in a single daily capsule. As NZ’s number one selling supplement brand — a claim backed by Circana NZ grocery and pharmacy value sales data — GO Healthy is widely available through Healthpost, Unichem, and health food stores, with pricing typically in the NZ$25-40 range. Check the form and the dose on the label; the range varies considerably between products.
Check the dose on this one before you buy it. 500mg of elemental magnesium in a single capsule sits above the 350mg daily upper limit that applies to magnesium from supplements and medicines, separate from what you eat. That limit is not arbitrary: going over it commonly causes diarrhoea, nausea and cramping. This is not a product to pick up as a casual everyday top-up. If you want routine maintenance, a lower-strength option will serve you better. If you have a specific reason to take 500mg, raise it with a pharmacist or GP first — and particularly so if your kidney function is reduced, because that is when magnesium can build up to genuinely harmful levels.
Best for: People who have a considered reason for a high single dose and have checked it with a clinician. Not a default everyday choice.
3. BePure Magnesium Restore — Best NZ Practitioner Brand
BePure’s Magnesium Restore powder delivers magnesium in a drinkable form that many people find easier to take than capsules. It uses magnesium bisglycinate — a highly absorbable, chelated form that is gentle on digestion — delivering 330mg of magnesium per serving, with a pleasant taste and easy dissolving. Available direct from BePure and from Healthpost at around NZ$35 for a 30-serve tub. Note that BePure also sells a Magnesium Restore in capsule form under the same name, which delivers 300mg per serving and adds L-carnitine — so check which one you are ordering.
Best for: People who prefer powders over capsules, and those wanting a practitioner-quality NZ product.
4. Sanderson Magnesium FX — Best Budget Pick
Sanderson is a long-established New Zealand brand — three generations of the Sanderson family have worked in the natural health industry since 1979. Their Magnesium FX tablets combine four organic forms of magnesium — amino acid chelate, citrate, aspartate and orotate — delivering 160mg of elemental magnesium per tablet. It is solid value for anyone who wants better-absorbed forms than oxide without paying glycinate prices. Worth knowing before you combine it with anything else: each tablet also carries 100IU of vitamin D3, 30mcg of selenium and 5mg of vitamin B6, which matters if you are already taking a separate vitamin D supplement. Available from NZ pharmacies and online retailers at around NZ$14.50 for 60 tablets and NZ$22.50 for 120 when checked in September 2026.
Best for: Those wanting better-than-oxide absorption at an affordable price point.
5. Thorne Magnesium Bisglycinate (via iHerb) — Best International Option
Thorne’s magnesium bisglycinate is one of the gold-standard international options for anyone ordering through iHerb. NSF Certified for Sport, and 200mg of elemental magnesium per serving across 60 servings (it is a drink powder, not capsules). Price depends on the exchange rate and iHerb’s shipping thresholds on the day, so check the landed cost rather than the shelf price before you order.
Best for: Those prioritising the highest available testing standards and comfortable with international ordering.
What the Label Will Not Tell You
The milligram number on the label is often the compound weight, not the elemental magnesium content. For example, 500mg of magnesium citrate delivers around 75-80mg of actual (elemental) magnesium. Always look for the elemental magnesium amount — this is what actually matters for dosing. Good NZ brands like Clinicians clearly state this; cheaper products often bury it.
Most adults need 310-420mg of elemental magnesium daily from all sources combined, food plus supplements — around 310-320mg for women and 400-420mg for men, depending on age. Magnesium-rich foods include dark leafy greens, pumpkin seeds, almonds, and dark chocolate. If you eat a varied diet with plenty of vegetables, you may already be getting 200-300mg from food and only need a modest top-up.
Taking too much magnesium (above 350mg supplemental per day for most people) can cause loose stools. Start with a lower dose and increase gradually.
When to Take Magnesium
Timing matters a good deal less than consistency. If a form sits better with you in the evening, take it in the evening — plenty of people do, and glycinate is the usual choice for it because it does not loosen the bowel at normal doses. Citrate and malate can be taken any time, though citrate’s effect on the bowel makes it the less convenient one last thing at night. The spacing that genuinely matters is with medicines rather than with other supplements: keep magnesium at least two hours away from oral bisphosphonates, and two hours before or four to six hours after tetracycline and quinolone antibiotics, because it reduces how much of those medicines you absorb.
The Bottom Line
For most people the sensible default is one of the organic forms — glycinate, bisglycinate or citrate — at a modest elemental dose, chosen on digestive tolerance and price rather than on absorption claims nobody can substantiate. If you want glycinate specifically, BePure and Thorne are the two options above that actually use it; the Clinicians product, good as it is, is aspartate. Read the elemental magnesium figure rather than the number on the front of the box, keep supplemental magnesium at or under 350mg a day unless a clinician has advised otherwise, and be wary of anything that is straight magnesium oxide unless the laxative effect is the reason you are buying it.
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Read the Elemental Magnesium, Not Just the Compound Weight
A label may advertise a large amount of magnesium glycinate or citrate while providing a much smaller amount of elemental magnesium—the amount that counts toward your intake. Compare products using the elemental-magnesium line on the nutrition panel and the number of capsules needed per serving. A transparent label also identifies the exact form rather than using a proprietary blend.
Which Form Fits Which Goal?
- Magnesium glycinate: often chosen when digestive tolerance is the priority. It is not a guaranteed sleep treatment, despite common marketing.
- Magnesium citrate: well absorbed and may loosen stools, which can be helpful or inconvenient depending on the person.
- Magnesium oxide: inexpensive and contains a high proportion of elemental magnesium, but it is less completely absorbed and commonly causes gastrointestinal effects.
- Magnesium chloride: another soluble option. Topical sprays are popular, but evidence that they reliably correct magnesium status through intact skin is limited. The same limitation applies to magnesium bath flakes and Epsom salt soaks.
Magnesium Glycinate and Citrate, Side by Side
Glycinate and citrate are the two forms most people end up choosing between, and both are reasonable choices. Each is magnesium bound to an organic molecule rather than the simple inorganic salt used in magnesium oxide, and both are absorbed more completely than oxide. What separates them is the molecule attached: glycine, an amino acid, in one case, and citric acid in the other. That attached molecule changes how the supplement behaves in the gut more than it changes how much magnesium you end up with.
| Factor | Magnesium glycinate | Magnesium citrate |
|---|---|---|
| Bound to | Glycine, an amino acid | Citric acid |
| Absorption | Better than oxide | Better than oxide |
| Effect on the gut | Usually well tolerated, with no laxative effect at normal doses | Draws water into the bowel, so it can loosen stools as the dose rises |
| Commonly chosen for | Daily use, evening use, sensitive digestion | A general top-up, and cases where a mild laxative effect is welcome |
| Cost in NZ | Higher | Lower to mid |
One thing worth saying plainly: there is very little head-to-head human research comparing these two forms directly, so anyone quoting a precise absorption percentage for either is going beyond the evidence. The published comparisons mostly measure organic forms against oxide rather than against each other. Tolerance, timing and price are the factors that will actually decide it for you.
Choosing Between the Two
Glycinate makes sense if you have a sensitive stomach, you want to take magnesium daily without thinking about it, or you plan to take it in the evening and would rather not risk a laxative effect overnight. It is the more expensive option, and what you are paying for is tolerance rather than a dramatic difference in how much magnesium gets absorbed.
Citrate makes sense if cost matters, your digestion is robust, or you would actively welcome the bowel-loosening effect. It is a genuine step up from oxide and is widely stocked in New Zealand pharmacies and health stores. If you do choose citrate, build up slowly rather than starting at the full label dose, and bear in mind that the same effect makes it less convenient as a nightly supplement.
Dose, Side Effects and Interactions
Start with food sources—nuts, seeds, legumes, whole grains and leafy greens—and use a supplement to fill a defined gap. The US National Institutes of Health sets an adult upper limit of 350 mg per day for magnesium from supplements and medicines, not including food, unless a clinician recommends otherwise. Higher supplemental amounts commonly cause diarrhoea, nausea or cramping.
Magnesium can interfere with absorption of some antibiotics and bisphosphonates, and kidney impairment can increase the risk of excess magnesium. Check timing with a pharmacist and seek personal advice if you have kidney disease, take regular medicine, are pregnant, or are supplementing for persistent symptoms. For a broader comparison of evidence and quality checks, visit our New Zealand supplement guide , and if sleep is your main reason for taking magnesium, our guide to the best sleep supplements in NZ.
Source
NIH Office of Dietary Supplements: Magnesium fact sheet for health professionals
