Last reviewed September 2026
Most experts take: Glycinate or L-threonate, in the evening, for sleep.
Best evidence: Blood pressure, blood sugar, migraine and constipation.
Weakest evidence: Sleep and cognition. No effect on cramps.
More likely to be short: People with gut conditions, type 2 diabetes or heavy alcohol use, older adults, and anyone on a PPI or diuretic.
On this page: Which form · What the experts take · Taken for vs shown to do · Do you need it, and how much? · How to choose
Which form to buy
Forms that dissolve well in liquid are absorbed better, and NIH names citrate, chloride, lactate and aspartate as more bioavailable than oxide and sulfate (NIH ODS). Whatever is not absorbed stays in the gut and loosens stools, so the form also decides the side effects.
| Form | Absorption | Pick it for | Note |
|---|---|---|---|
| Glycinate (bisglycinate) – most common expert pick | Not in NIH’s comparison; dissolves well | Sleep, general top-up | The most common expert pick. Around $0.10 per 100 mg. |
| L-threonate | Not in NIH’s comparison | Sleep, cognition | Raised brain magnesium in a 2010 rat study. Around ten times the price of glycinate. |
| Citrate | Higher (NIH) | Constipation, general | Loosens stools at higher doses; Hyman uses 150-300 mg short-term for that. |
| Chloride (SlowMag) | Higher (NIH) | Daytime top-up | Attia’s daytime form. |
| Oxide | Lower (NIH) | Only if you already have it | More passes through unabsorbed, but it is the form used in several sleep, migraine and constipation trials. |
What the experts take
Every row links to the Fast Life Hacks article that documents it, with the podcast or video source.
| Expert | Form | Dose | Brand |
|---|---|---|---|
| Andrew Huberman | L-threonate (or glycinate) | 145-250 mg | None named; now AG1’s AGZ blend |
| Peter Attia | Oxide/citrate + chloride + L-threonate | ~700 mg/day across all three | Jarrow, SlowMag, Carlson |
| Rhonda Patrick | Glycinate | 120 mg (rest from diet) | Pure Encapsulations |
| Mark Hyman | Glycinate | 400-500 mg | Pure Encapsulations, Designs for Health |
| Gary Brecka | 7-form blend | Per label | BiOptimizers Magnesium Breakthrough |
| Tim Ferriss | L-threonate | 144 mg | Not stated |
| Eric Berg | Glycinate | Not stated (calls 400 mg a baseline) | Own brand |
| Stacy Sims | L-threonate | 200-400 mg general guidance | Momentous Nightly Sleep |
| Bryan Johnson | Citrate | 150 mg | Blueprint Longevity Mix |
| Kevin Rose | L-threonate | Per label | Jarrow MagMind |
Taken for vs shown to do
The experts’ reasons and the trial evidence do not line up. Rows run from the best-supported outcome to the least.
| Outcome | Who takes it for this | What the trials show |
|---|---|---|
| Constipation | Hyman, Attia | ✅ Works. A 2019 placebo-controlled trial of magnesium oxide improved chronic constipation. |
| Blood pressure | Nobody on this list | ✅ Solid but small. A meta-analysis of 34 trials: about 2 mmHg lower at roughly 370 mg a day, more in people who started low. |
| Blood sugar | Hyman | ✅ Solid in the right people. A 2016 meta-analysis found lower fasting glucose and insulin resistance, mainly in people with diabetes, prediabetes or low magnesium. |
| Migraine | Nobody on this list | ✅ Fewer attacks. A 2016 meta-analysis found oral magnesium reduced migraine frequency. |
| Sleep | Huberman, Ferriss, Attia, Brecka, Sims, Berg | ⚠️ Weak. A 2024 systematic review found small gains in self-reported sleep, mostly in older adults and low-intake groups, from short trials with few participants. Not a sedative. |
| Cognition (threonate) | Huberman, Ferriss, Rose | ⚠️ Weak. One 2024 trial in 80 adults with sleep complaints, funded by the manufacturer. Rodent data behind the rest. |
| Muscle cramps | Berg (night cramps) | ❌ No effect. A 2020 Cochrane review found magnesium unlikely to help night or exercise cramps. |
Do you need it, and how much?
Many Americans get less magnesium than the RDA (NIH ODS); one analysis of national intake data puts it at roughly half. NIH names four groups at higher risk of running short:
- Gastrointestinal disease such as Crohn’s or coeliac disease, which cuts absorption.
- Type 2 diabetes, which raises magnesium loss in urine.
- Heavy drinking. NIH lists alcohol dependence specifically.
- Older adults, with men over 70 the group most likely to have low intake.
Patrick takes only 120 mg because leafy greens, nuts and legumes cover the rest, which is the NIH position too: food first. A standard blood test is a poor guide, because less than 1% of the body’s magnesium is in the blood (NIH).
Dose figures from the NIH Office of Dietary Supplements:
| Figure | Note | |
|---|---|---|
| Typical supplemental dose | 150-400 mg elemental | Check the label for elemental magnesium, not the weight of the compound. |
| RDA (food + supplements) | 400-420 mg men, 310-320 mg women | |
| Upper limit for supplements | 350 mg/day | Set on the diarrhoea threshold, not toxicity; food magnesium is not counted. Several experts above exceed it. |
| When | Evening for sleep; with food otherwise | Huberman, Ferriss and Attia take it 30-60 minutes before bed. |
Doses are what studies and experts used, not advice for you. See the medical disclaimer.
Medicines. Two lower magnesium status, per NIH: diuretics and proton pump inhibitors (omeprazole and similar). For PPIs, a 2019 meta-analysis found long-term users had higher odds of low magnesium. NIH also lists three drug classes that magnesium interferes with in the gut:
- Tetracycline and quinolone antibiotics (doxycycline, ciprofloxacin). Take the antibiotic at least 2 hours before or 4-6 hours after magnesium.
- Oral bisphosphonates for osteoporosis (alendronate). Keep them at least 2 hours apart.
Two further points follow from the evidence table above rather than from a warning list. Magnesium lowers blood pressure and blood glucose a little, so anyone on blood pressure or diabetes medication should mention it to their prescriber. And NIH notes that the kidneys control magnesium balance and clear the excess, so with reduced kidney function ask a doctor before supplementing at all.
How to choose a product
Pick a product with third-party testing (NSF, USP or Informed Sport marks) and a stated elemental magnesium figure per capsule. Ignore “7 forms in one” marketing: the total elemental dose is what matters.
Reputable brands of magnesium include:
Magnesium glycinate
| Product | Capsules | Price | Cost per 100 mg* |
| Nutricost - Mag. Glycinate | 360 x 70 mg | $22 | $0.09 |
| NOW - Mag. Glycinate | 180 * 100 mg | $20 | $0.11 |
| California Gold Nutrition - Mag. Glycinate | 180 x 133 mg | $25 exc. coupon | $0.10 |
Magnesium L-threonate
| Product | Servings | Cost per 100 mg |
| 30 x 144 mg | $1.16 | |
| Nutricost - L-Threonate | 30 * 150 mg | $1.10 |
| Life Extension - L-Threonate | 50 x 144 mg | $0.71 |
Roundup
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Disclaimer: The above information is for research and educational purposes only and not a substitute for professional medical advice. See full medical disclaimer.
Note: We have no affiliation with the experts listed here - this page is based on publicly shared information.