Magnesium glycinate: the one form that actually works.

§.01The short answer.

If you want one sentence: buy magnesium bisglycinate at 200 mg elemental per capsule, take one or two with dinner. That's it. That's the recommendation. It's well-absorbed, it's the gentlest form on the gut, and it delivers the mineral in the chemical environment your body actually uses.

The rest of this guide exists because the magnesium aisle is a disaster of marketing — oxide for pennies, threonate for $60, "seven-in-one complexes" that deliver none of anything in a useful dose. You don't need seven magnesiums. You need enough of the right one.

Magnesium is the fourth most abundant mineral in the body and roughly half of US adults fall short of the RDA through diet. The deficit is real. The solution is boring. — Liv Hartwell, PharmD

§.02Why glycinate, not the other nine.

Every magnesium supplement is a magnesium ion paired with a carrier molecule. The carrier determines absorption, tolerability, and — for threonate specifically — whether the mineral crosses into the brain. Here's the honest comparison.

For 90% of people asking "should I take magnesium for sleep / stress / cramps / deficiency correction," the answer is glycinate. For the specific niche of cognition in older adults, threonate becomes defensible. For the rest — oxide is mostly a waste and the multi-form blends are a way to charge more without delivering more.

§.03Dose, timing, and stacking.

The RDA for adults is 310–420 mg of elemental magnesium per day, most of which should come from food — leafy greens, legumes, nuts, whole grains, dark chocolate. A supplement is there to close the gap, not to replace the diet. For most supplementing adults, 200–400 mg of elemental magnesium is the useful range.

A protocol that works for most people.

• Start: 200 mg elemental magnesium, one capsule, with dinner.
• Build (if needed): After a week, add a second capsule. Most people don't need to.
• Ceiling: Stay under 400 mg supplemental elemental magnesium unless you have a specific medical reason. Above that you'll likely get loose stools.
• With food or fasted? With food, always. Glycinate is gentle enough fasted, but food improves tolerability without hurting absorption.
• Morning or night? Night. Magnesium is mildly sedative. The RCT data leans toward evening dosing for sleep effects.

§.04What the trials show for sleep, stress, cramps.

The mechanism is plausible — magnesium modulates GABA and NMDA receptor activity, which is why it feels calming. The clinical effects are real but small. Be suspicious of anyone selling this as a miracle.

Sleep.

Two meta-analyses (2021, 2023) pooling RCTs in older adults found statistically significant but modest reductions in sleep-onset latency — roughly 7 to 17 minutes faster to fall asleep versus placebo. Effect sizes were larger in adults with baseline insufficiency. Not a sleeping pill. A mild nudge for people with a reason to be deficient.

Anxiety and stress.

A 2017 systematic review found suggestive evidence for anxiety reduction in mild anxiety and PMS-related anxiety, stronger when paired with B6. The clinical signal is weaker than the sleep signal. Treat as plausible but unproven as a standalone anxiolytic.

Muscle cramps.

This is where the evidence is most disappointing. Cochrane-style reviews find no clear benefit for idiopathic leg cramps in otherwise-healthy adults. The exception is pregnancy-related leg cramps, where some RCTs show benefit. If your cramps are deficiency-driven, supplementation helps. If they're not, it probably won't.

§.05Side effects and who should skip it.

• Loose stools. Dose-dependent. Glycinate is the least likely form to cause this; oxide and citrate are the worst. If you get diarrhea, drop the dose.
• Drug interactions. Magnesium binds some antibiotics (tetracyclines, fluoroquinolones) and thyroid medication in the gut. Separate by at least 2 hours.
• Kidney disease. The kidneys clear excess magnesium. If yours don't work well, you can accumulate. Check with a clinician before supplementing.
• Bowel obstruction or severe heart block. Contraindicated. Rare, but worth flagging.
• Pregnancy and nursing. Generally safe at recommended doses; bisglycinate is the preferred form. Discuss with your OB if supplementing above 400 mg.

§.06What to look for on a label.

1. Elemental magnesium in mg, listed separately. If you only see "magnesium bisglycinate 1400 mg," do the math or assume the brand is hiding it.
2. Bisglycinate or diglycinate chelate — not "magnesium glycinate complex." A true chelate has the mineral bound to two glycine molecules. "Complex" is a marketing word that can mean anything.
3. Third-party tested. USP, NSF, Informed Choice. In the US, supplement testing is voluntary. Brands that don't test are telling you something.
4. No "proprietary blend." If the Mg dose is inside a proprietary blend, you don't know how much you're getting. Walk away.
5. Small number of ingredients. Magnesium + a capsule shell. Maybe vegetable cellulose. That's it. If the ingredient list runs to eight lines, you're paying for filler.

§.07Frequently asked, plainly answered.

§.08The bottom line.

Magnesium bisglycinate is one of the most useful, most over-complicated supplements in the apothecary. The rule is simple: buy the glycinate form, read the elemental weight, take 200 mg with dinner, and judge after a month. If you're not sleeping better, cramping less, or feeling calmer — magnesium wasn't the missing piece. Add it to your "tried, moving on" list and save the money.

If you'd like to try ours, it's $28 for sixty capsules, 200 mg elemental per cap, USP-tested, in a vegetable capsule. No blend, no filler, no extras you didn't ask for.