Magnesium Glycinate 400 mg: What a Serving Really Delivers
“400 mg magnesium glycinate” can mean two doses. If the Supplement Facts line named Magnesium says 400 mg, that is 50 mg over NIH’s 350 mg a day limit for pills, so take part of the serving. If 400 mg is the weight of the compound, it holds only about 56 mg of magnesium. Of the 149 glycinate labels we read, 32.9% give 400 mg or more in one serving.
A dose under the limit
Every price on this page is at brand list prices; prices on Amazon differ. List prices checked October 14, 2026.
The two 400s: compound weight vs magnesium
Magnesium glycinate is one magnesium bound to two glycines. Magnesium is about 14.1% of its weight. So a capsule with 400 mg of the compound holds about 56 mg of magnesium, and a serving with 400 mg of magnesium needs about 2,840 mg of the compound. That is why 400 mg servings are 3 or 4 tablets or a scoop of powder. The “Magnesium” line on the Supplement Facts panel is the magnesium itself (the elemental amount), not the weight of the whole compound (NIH).
Is 400 mg of magnesium the right dose?
No, not from pills. The upper limit for adults is 350 mg a day of magnesium from supplements and medicines. Food does not count toward it (NIH). Adults need 310 to 420 mg a day from food and pills together. Sleep trials of plain magnesium used 250 to 729 mg of magnesium a day, including a 2025 trial of 250 mg as glycinate (Schuster 2025). Trials of magnesium L-threonate are separate: they used 1 to 2 g of the compound, about 72 to 144 mg of magnesium.
A label that directs 400 mg or more a day, and how to stay under the limit:
- KAL Magnesium Glycinate 350 mg: 350 mg in 4 capsules: the whole daily limit in one serving, so count any other pills that contain magnesium.
If you have kidney disease, ask your doctor before you take magnesium. Weak kidneys cannot clear the extra, so it can build up (NIH).
Every magnesium glycinate we track, by cost per 300 mg
300 mg of magnesium is a dose under the limit, so we compare cost on it. The last column shows how many capsules or tablets you can take and stay at or under 350 mg. Cheapest first; products with no list price come last.
| Product | Per 300 mg | Most a day under 350 mg | Buy |
|---|---|---|---|
| BulkSupplements Magnesium Glycinate Powder300 mg of magnesium in ¾ teaspoon, list $21.97NSF/ANSI 173 · a glycinate + oxide blend | $0.19 | Measure the powder | Check price |
| Nutricost Magnesium Glycinate 210 mg210 mg of magnesium in 3 capsules, list $24.97No testing list found | $0.30 | 5 capsules (350 mg) | Check price |
| Doctor's Best High Absorption Magnesium200 mg of magnesium in 2 tablets, list $23.99No testing list found | $0.30 | 3 tablets (300 mg) | Check price |
| NOW Magnesium Bisglycinate Powder300 mg of magnesium in 1 level teaspoon, list $23.99No testing list found | $0.32 | Measure the powder | Check price |
| Revive MD Pure Magnesium Glycinate 200 mgOur pick200 mg of magnesium in 2 capsules, list $19.99Informed Sport | $0.50 | 3 capsules (300 mg) | Check price |
| NOW Magnesium Glycinate 200 mg200 mg of magnesium in 2 tablets, list $31.99No testing list found | $0.53 | 3 tablets (300 mg) | Check price |
| Thorne Magnesium Glycinate120 mg of magnesium in 1 capsule, list $26.00NSF/ANSI 173 | $0.72 | 2 capsules (240 mg) | Check price |
| Nature Made Magnesium Glycinate 200mg200 mg of magnesium in 2 capsules, list $21.99USP Verified | $1.10 | 3 capsules (300 mg) | Check price |
| Nature's Bounty High Absorption Magnesium Glycinate 240 mg240 mg of magnesium in 2 capsulesNo testing list found · no list price we could check | – | 2 capsules (240 mg) | Check price |
| KAL Magnesium Glycinate 350 mg350 mg of magnesium in 4 capsulesNo testing list found · no list price we could check | – | 4 capsules (350 mg) | Check price |
Our pick is Revive MD Magnesium Glycinate: 200 mg of magnesium in 2 capsules, on the Informed Sport list, $0.33 a day at Revive MD’s own price. On the Informed Sport list: every batch is tested for drugs banned in sport. It is not a check of the label. Its label serving is 2 capsules; 3 capsules (300 mg) is the most that stays under the limit.
We read 149 glycinate labels: 400 mg is not the typical serving
From 827 labels sold as magnesium glycinate (NIH label database, August 27, 2026), 149 list glycinate or bisglycinate on the Supplement Facts panel. The median serving gives 250 mg of magnesium and the median capsule or tablet 111 mg. 32.9% give 400 mg or more in one serving, and 78.5% need 2 or more capsules for a serving.
| Item | Value (mg) |
|---|---|
| Median per capsule or tablet | 111 mg |
| Median per serving | 250 mg |
| NIH limit for pills | 350 mg |
| A “400 mg” serving | 400 mg |
How we read the labels
827 labels sold as magnesium glycinate were pulled from the NIH Dietary Supplement Label Database on August 27, 2026; the 149 that list glycinate or bisglycinate on the Supplement Facts panel were read. We split the labels into two groups and print only figures that came out the same in both. Download the data (JSON) (CC BY 4.0).
Frequently asked questions
Does "400 mg magnesium glycinate" mean 400 mg of magnesium?
Only if the Supplement Facts line named Magnesium says 400 mg. Magnesium glycinate is about 14.1% magnesium by weight, so 400 mg of the compound holds about 56 mg of magnesium, and 400 mg of magnesium takes about 2,840 mg of the compound. The front of the bottle can print either number.
Is 400 mg of magnesium glycinate too much?
400 mg of magnesium from pills is 50 mg over NIH’s 350 mg a day limit for adults; above it, diarrhea becomes more common. Take part of the serving instead, and ask your doctor first if your kidneys are weak. 400 mg of the compound (about 56 mg of magnesium) is far under the limit.
How many capsules is 400 mg of magnesium glycinate?
Of the 149 glycinate labels we read, the median capsule or tablet holds 111 mg of magnesium, so 400 mg is usually 4 or more. 78.5% of labels need 2 or more capsules for one serving. Count the magnesium per capsule and stop at 350 mg a day.
What is the cheapest way to get a dose under the limit?
At list prices, the lowest cost capsule or tablet of pure glycinate we price is Nutricost Magnesium Glycinate 210 mg, $0.30 per 300 mg of magnesium. Prices on Amazon differ.
Does glycinate absorb better than other forms?
In the one trial that compared glycinate with oxide at the same dose (100 mg, in 12 people who had part of their small bowel removed), overall absorption was about the same (23.5% vs 22.8%), and glycinate was better tolerated by every patient (Schuette 1994). Small studies found the citrate, aspartate, lactate and chloride forms absorbed better than oxide and sulfate (NIH). NIH says nothing about glycinate either way.
How much to take by age: how much magnesium glycinate to take · magnesium dosage guide.
Related
- Best magnesium glycinate · cheapest magnesium glycinate · side effects
- Glycinate vs citrate · magnesium guide
Sources
- NIH Office of Dietary Supplements. Magnesium fact sheet for health professionals (updated January 6, 2026): RDA and the 350 mg limit for supplements.
- Schuette SA, Lashner BA, Janghorbani M. Bioavailability of magnesium diglycinate vs magnesium oxide in patients with ileal resection. JPEN. 1994. PubMed 7815675
- Schuster J, et al. Magnesium bisglycinate supplementation in healthy adults reporting poor sleep. Nat Sci Sleep. 2025. PubMed 40918053; Mah J, Pitre T. BMC Complement Med Ther. 2021. PubMed 33865376
- NIH Dietary Supplement Label Database. dsld.od.nih.gov (labels read August 27, 2026).
- Prices: each brand’s own list price, checked October 14, 2026. We quote no Amazon prices.
This page is for information. It is not medical advice.