Magnesium bisglycinate is magnesium bound to two molecules of glycine, a small amino acid. "Magnesium glycinate" usually means the same thing, so the more useful question is how much actual magnesium is in a serving. The label number you see first can be the weight of the whole compound, and only 11 to 14% of that is magnesium.
This post covers what the name means, how to read a magnesium label, what the research says about how well each form is absorbed, and where most of your magnesium comes from.
Contents
- The short version
- What magnesium bisglycinate is
- Glycinate vs bisglycinate: are they the same?
- How to read the label
- Why people choose it, and what the evidence says
- Magnesium and sleep
- Food first
- Does coffee use up your magnesium?
- Where it fits in Uncaffed
The short version
Magnesium bisglycinate is one magnesium bound to two glycine molecules, and glycinate is usually another name for it. By weight it is 11 to 14% magnesium, so a "500 mg" serving of the compound holds about 55 to 70 mg of magnesium. The figure that counts is the elemental magnesium, set against a daily reference value of 375 mg. Studies do not show that bisglycinate is absorbed better, or worse, than other forms in healthy adults. Most people can get a large share of their magnesium from spinach, nuts and wholemeal bread.
What magnesium bisglycinate is
Magnesium is a mineral, and in a supplement it is bound to a partner molecule. The partner is called the form, and it decides what the powder is called. Oxide, citrate and chloride are common forms.
In bisglycinate the partner is glycine. Each magnesium is bound to two glycines, which is where "bis" comes from. Because the magnesium is held by the amino acid in this way, the ingredient is described as a chelate. A 1994 clinical paper calls it "magnesium diglycinate (chelate)", which is the same arrangement under a different name (Schuette et al., 1994).
Glycinate vs bisglycinate: are they the same?
Usually, yes. Ingredient suppliers list the powder as magnesium bisglycinate. The 1994 paper calls it diglycinate. Plenty of retail products say glycinate. We did not find a trial that compares products sold under the different names.
What does vary from one product to the next is how much magnesium each serving holds. That is worth checking before you compare prices.
How to read the label
A magnesium label can show two different numbers.
- The weight of the compound, for example "magnesium bisglycinate 500 mg".
- The weight of the magnesium in it, usually written as "elemental magnesium" or just "magnesium".
The second number is the one that counts. Pure magnesium bisglycinate is about 14% magnesium by weight, which is our arithmetic from the formula. Ingredient suppliers' specifications run from about 11 to 14.5%. So 500 mg of the compound holds about 55 to 70 mg of magnesium.
The daily reference value used on UK labels is 375 mg of magnesium (Regulation 1169/2011, Annex XIII, as retained). The NHS gives the amount adults need as 300 mg a day for men and 270 mg for women aged 19 to 64 (NHS). Against either figure, a serving labelled "500 mg" of bisglycinate is a modest amount of magnesium.
Compare the elemental magnesium per serving. The weight of the powder tells you much less.
Why people choose it, and what the evidence says
Magnesium oxide is one of the most common forms, and in the studies that compared forms it absorbed poorly. A 2001 study measured the rise in urinary magnesium in healthy volunteers and put fractional absorption of oxide at about 4%. Chloride, lactate and aspartate were higher and similar to each other (Firoz and Graber, 2001). High doses cause trouble too. The NHS says taking more than 400 mg of magnesium for a short time can cause diarrhoea. Those are the reasons usually given for choosing an amino-acid form such as bisglycinate.
For bisglycinate itself the evidence is small and mixed:
- In 1994, 12 people who had had part of their small intestine removed took a labelled 100 mg dose of this form and of oxide. Overall absorption was the same, 23.5% and 22.8%. In the four who absorbed oxide worst, bisglycinate absorbed better, 23.5% against 11.8% (Schuette et al., 1994). These were patients, not healthy adults.
- In 2003, 46 healthy people took 300 mg a day of citrate, an amino-acid chelate or oxide for 60 days. Both organic forms beat oxide on urinary magnesium, and citrate gave the highest blood level. The abstract does not say the chelate was bisglycinate (Walker et al., 2003).
- In 2024, 40 healthy people took one dose each of four forms. Blood magnesium rose with oxide after an hour and citrate after four hours, with no significant rise for bisglycinate at any point in six hours. The authors work for ingredient companies, and a company that makes a competing product funded the study (Pajuelo et al., 2024).
A 2017 review pulled the literature together. It found that the type of magnesium salt appears less relevant than is often thought. The dose, the food it is taken with and the person matter too, and the review said it remains unclear which form is best (Schuchardt and Hahn, 2017).
Studies do not show that bisglycinate is absorbed better than other forms in healthy adults. They do not show that it is worse either.
Magnesium and sleep
Magnesium is commonly used to support sleep, but the evidence is mixed. A 2026 review of 12 randomised trials of oral magnesium found inconsistent results across the ways sleep was measured, and rated the certainty of the evidence low to very low (Lopresti et al., 2026). The trials used many different forms and doses.
We make no sleep claims for magnesium, and none for Flow.
Food first
The NHS says magnesium is found in a wide variety of foods, including spinach, nuts and wholemeal bread. It also says that taking 400 mg or less a day of magnesium from supplements is unlikely to cause any harm.
One easy way to see where you stand is to look at what you ate yesterday. Spinach in a meal, a handful of nuts and a slice of wholemeal bread are the foods the NHS names. Nothing needs buying for that.
Does coffee use up your magnesium?
You will see this claim often. The evidence is small, and the numbers are small too.
One controlled study put 17 healthy adults on a fixed diet in a metabolic ward and gave them caffeine at 3 mg per kilogram of lean body mass at 7am and again at 10am, a large amount in one morning. They passed more magnesium in their urine for six hours after the second dose, then less overnight. The net extra loss over 24 hours was 0.16 mmol (Kynast-Gales and Massey, 1994). That is about 3.9 mg of magnesium by our arithmetic, roughly 1% of the 375 mg reference value.
Coffee also contains magnesium. A 2021 review calculated that one portion of coffee can cover about 6.4 to 7.5% of the daily requirement, and that three or four cups could be a meaningful source (Olechno et al., 2021). We did not find a recent study showing that people who drink coffee have low magnesium.
If you drink a lot of coffee, the caffeine calculator adds up where your day stands, and how long caffeine stays in your system covers the timing.
Where it fits in Uncaffed
As a nutrient, magnesium contributes to a reduction of tiredness and fatigue. The Uncaffed 30-day reset kit has two parts, and the magnesium is in Flow, not Reset.
- Flow has no added caffeine and runs for all 30 days. It contains magnesium as bisglycinate: 50 mg of elemental magnesium per capsule, so 100 mg across the two daily capsules, which is 27% of the 375 mg reference value.
- Reset steps your caffeine down from 160 mg a day to none over 20 days, five days at each step, with L-theanine alongside.
- For the 30 days, the capsules are your only caffeine. Decaf, herbal tea and rooibos keep the ritual going.
Heavy caffeine user? If you have more than about 400 mg a day from all sources, try to cut down a little before you start. Dropping straight to the kit's starting level can be a big change if you're not prepared for it. Not sure how much you have? The calculator adds it up. Everyone else can start straight away.
Preorders are open. Kits ship 30 November, UK only. The kit page has the full details, the quiz helps you find your starting point, and the science page explains how the steps were chosen. The kit is not for under-18s or anyone pregnant or breastfeeding.
