Magnesium is one of the most-recommended supplements in our pharmacy — but the form matters more than most people realise. Glycinate, citrate, malate, threonate, oxide — they're not interchangeable. Here's what each does best.
Magnesium is involved in over 300 enzymatic reactions in the body. It supports nerve and muscle function, blood pressure regulation, blood sugar control, protein synthesis, bone formation, and energy production. Studies estimate 30–50% of UK adults don't get the daily intake from food.
The catch is that "magnesium" on a supplement label could mean any of a dozen different chemical compounds, each with different absorption, different tissue distribution, and different practical effects. The wrong form for what you're trying to support is often why people think "magnesium doesn't work for me."
This is a pharmacist's straight guide to which form does what.
Why the form matters: bioavailability and tissue targeting
Magnesium has to bind to something to be stable as a supplement. That binding partner is the "form":
- Glycinate — bound to the amino acid glycine
- Citrate — bound to citric acid
- Malate — bound to malic acid
- L-Threonate — bound to a metabolite of vitamin C
- Taurate — bound to the amino acid taurine
- Oxide — bound to oxygen (cheapest, least bioavailable)
- Chloride — bound to chloride ions
- Sulphate — Epsom salts, used externally
The binding partner affects two things: how well the magnesium absorbs across the gut wall, and where in the body it ends up doing its work. The amino-acid-bound forms (glycinate, taurate) are absorbed via amino acid transport channels and tend to reach calmer, nervous-system-focused destinations. Acid-bound forms (citrate, malate) are absorbed differently and have more digestive and metabolic activity. Threonate uniquely crosses the blood-brain barrier.
Magnesium glycinate — for sleep, stress and nervous-system support
If we're recommending magnesium to someone for the first time and they don't have a specific other need, this is what we reach for.
Best for: sleep onset and quality, evening calm, restless legs, generalised muscle tension, anxiety modulation, recovery from training.
Why: the glycine half is itself a calming, sleep-promoting amino acid. It binds to NMDA receptors and helps lower core body temperature at night, which is part of how the body initiates deep sleep. Combine that with magnesium's role in GABAergic signalling and you get the most calming form by a reasonable margin.
Dose: typically 200–400 mg elemental magnesium in the evening, about an hour before bed.
Tolerance: rarely causes digestive upset. Suitable for sensitive stomachs.
Pharmacist tip
Sleep-onset insomnia and 4am wake-up insomnia are different problems. Magnesium glycinate is especially good for the second — early-morning waking with a racing mind. Take it just before bed rather than at dinner for that pattern.
Magnesium citrate — for digestion and bowel regularity
The form most pharmacy clients ask for once they understand it.
Best for: mild constipation, sluggish digestion, supporting overall magnesium status when the gut is the bottleneck.
Why: citrate has a mild osmotic effect in the bowel, drawing water in and softening stools without being a stimulant laxative. Used in the right dose, it gently keeps you regular. Used in too high a dose, it'll do more than you want.
Dose: 200–400 mg elemental in the evening. Start lower and work up — some people are very sensitive.
Tolerance: can cause loose stools if you take too much. That's a feature for constipation, a bug for everyone else.
Magnesium malate — for energy and fibromyalgia-style fatigue
The "energy" magnesium.
Best for: chronic muscle fatigue, fibromyalgia symptoms, post-viral or chronic-fatigue-style depletion, low daytime energy with no obvious cause.
Why: malic acid is an intermediate in the Krebs cycle — the cellular energy production pathway. Combining it with magnesium gives you both the cofactor for ATP production and a substrate for it. The clinical evidence is modest but consistent for fatigue states.
Dose: 300–600 mg elemental, taken in the morning and lunch. Don't take it close to bedtime — it can be mildly energising.
Tolerance: usually well-tolerated. Less constipating than oxide, less laxative than citrate.
Magnesium L-threonate — for cognition and brain health
The newest form on the market, with growing interest in neurological applications.
Best for: cognitive function, memory, age-related neurological decline, supporting recovery from concussion or stress-induced cognitive issues.
Why: threonate is the only form that meaningfully crosses the blood-brain barrier and raises magnesium concentrations in cerebrospinal fluid. Animal studies show improvements in synaptic plasticity and memory; human evidence is still emerging but the mechanism is real.
Dose: the proprietary Magtein form delivers about 144 mg elemental at 2 grams of the threonate compound.
Tolerance: well-tolerated but more expensive. Worth it if cognitive support is your specific goal; otherwise glycinate is more cost-effective.
Magnesium taurate — for cardiovascular support
Less talked-about but worth knowing.
Best for: blood pressure support, cardiovascular health, palpitations or atrial-fibrillation risk reduction (with medical supervision), arrhythmia-prone individuals.
Why: taurine itself supports cardiac function and has independent blood-pressure-lowering effects. Combined with magnesium, it's a useful cardiovascular-targeted form.
Dose: 200–400 mg elemental once or twice daily.
Magnesium oxide — the one to avoid
Cheap, common in bargain multivitamins, and largely useless beyond a small laxative effect.
Absorption is in the 4–10% range — most of what you take goes straight through you. If you've ever taken a "magnesium" supplement and felt nothing, there's a high chance it was oxide. It exists because it's the cheapest possible binding partner; that's the only reason.
Magnesium chloride and sulphate
Chloride is sometimes used topically (sprays, bath flakes) — absorption through skin is modest but real. Sulphate is Epsom salts, used in baths for muscle soreness. Neither is a typical oral supplement choice.
How to combine forms
It's reasonable to use two forms simultaneously when goals differ:
- Glycinate at night + malate in the morning — sleep support and daytime energy.
- Glycinate at night + citrate as needed — sleep plus occasional bowel support.
- Threonate + glycinate — cognition during the day, sleep at night.
Total elemental magnesium across all sources should rarely exceed 600 mg/day from supplements without specific clinical reason. UK NICE guidance suggests 300 mg/day from food as a baseline, with supplemental adding to that for symptomatic support.
What this means for you
If you've taken magnesium and felt nothing, check the label — you were probably on oxide. For most people starting out, glycinate is the best default. Add citrate if you have digestive issues, malate if your problem is daytime energy, threonate if you're focused on cognition, taurate if you have cardiovascular concerns.
If you'd like a tailored magnesium recommendation, start a free consultation with our pharmacy team.
