Magnesium Glycinate vs Citrate: What’s the Difference?

Glycinate and citrate are two of the forms you’ll see most often on magnesium labels. Both deliver the same mineral. What changes is the molecule the magnesium is attached to, and that has a few practical consequences. Most of them are smaller, and less well studied, than the marketing around these products suggests.

Two different partner molecules

Magnesium glycinate, often labelled bisglycinate or glycinate chelate, is magnesium bound to glycine, an amino acid. Magnesium citrate is magnesium combined with citric acid.

Both are what chemists call organic forms, meaning the partner molecule is carbon-based. It isn’t a quality label. It simply separates them from inorganic forms such as magnesium oxide, and, as you’ll see below, that distinction turns up in the research.

How much of each is magnesium

The partner molecule adds weight, so only part of each compound is magnesium. Working from the molecular weights listed in PubChem:

Real ingredients can differ from these figures, because some contain water and some products mix several forms. Even so, the table explains why glycinate and citrate products need noticeably more powder per milligram of magnesium than oxide does.

On a US label you don’t have to do this sum yourself. The FDA requires the Supplement Facts panel to state the weight of the mineral, not of the compound, so “200 mg” means 200 mg of magnesium whichever form supplies it. Our guide to reading a Supplement Facts label covers the rest of the panel.

What the absorption research shows

Most studies of magnesium forms measure bioavailability: how much of the mineral reaches the bloodstream, or appears in urine, after a dose.

A 2021 systematic review brought together 14 studies that compared forms. The authors concluded that inorganic forms appear to be less bioavailable than organic ones, and that the percentage absorbed depends on the dose. They also noted that all the forms could keep magnesium at normal levels in healthy people who weren’t deficient to begin with.

That finding separates oxide from citrate. It says far less about glycinate versus citrate, because both fall on the same side of the line. Direct comparisons between those two are thin:

• A 2024 crossover study gave 40 healthy adults single doses of several magnesium sources, including citrate and bisglycinate, and tracked blood levels for six hours. Levels rose significantly at some time points after citrate, but not after bisglycinate. The study was funded by Lubrizol Life Science, the company behind the proprietary microencapsulated magnesium ingredient being tested, and two of the authors were Lubrizol employees. As an acute, single-dose study over six hours, it says little about regular, long-term use.
• A 2019 study in mice compared citrate, glycinate and other organic forms and found different patterns in different tissues. Results in animals don’t transfer neatly to people.

A third study makes a point that may matter more than the name of the form. In a 2019 study, 15 commercially available magnesium products showed very wide differences in dissolution and bioaccessibility in laboratory models. Two formulations with contrasting laboratory results were then tested in 30 people, and the one that performed poorly in the laboratory also showed lower bioavailability in the body. How a product is made, not just which form it contains, seems to count.

Citrate’s second job

Magnesium citrate isn’t only a supplement ingredient. It is also sold as an over-the-counter laxative: MedlinePlus describes it as a saline laxative, which works by keeping water in the stool. The same entry advises taking other medicines at least two hours before or after a magnesium citrate laxative.

A citrate supplement isn’t the same thing as a laxative product, but loose stools are a known effect of high magnesium intake in general. The NHS notes that taking more than 400 mg of magnesium for a short time can cause diarrhoea.

Glycinate is often marketed as gentler on the stomach. One small 2024 study that compared both citrate and bisglycinate, the industry-funded study described above, also recorded gastrointestinal side effects, but it wasn’t designed to settle which form is gentler. On the evidence available, “gentler” is a marketing claim rather than an established difference.

Glycinate and sleep

Glycinate is also widely promoted for sleep. In a 2025 randomised, placebo-controlled trial, 155 adults who reported poor sleep took either magnesium bisglycinate or a placebo. After four weeks, scores on a standard insomnia questionnaire had improved slightly more in the magnesium group. The authors described the benefit as modest, the statistical effect size was small, and they called for longer studies using objective sleep measurements. The trial itself was funded by the Institute of Food and One Health at Leibniz University Hannover. One author disclosed managing a contract research organisation that receives research funding from nutraceutical companies, and having received presentation honoraria from such companies.

The trial compared bisglycinate with a placebo, not with citrate, so it can’t tell you whether one form does better than the other.

So which is “better”?

It depends on the question, and research doesn’t settle most of them yet. What can be said with reasonable confidence:

• Both are organic forms. The 2021 systematic review found organic forms generally more bioavailable than inorganic ones such as oxide, but that does not establish that glycinate is better absorbed than citrate.
• Both need more compound than oxide per milligram of magnesium, so capsules or servings tend to be larger.
• Citrate also has a laxative use. Glycinate’s reputation for being gentle and for helping sleep rests on limited evidence.
• Quality varies widely between products, whatever form they use.

If you’re comparing actual products, our guide to comparing magnesium supplement labels shows how to line them up on magnesium per serving, form and price.

Whether a supplement makes sense at all depends on diet and health. The NHS says you should be able to get all the magnesium you need from a varied and balanced diet. For anyone taking regular medication or managing a health condition, a pharmacist or doctor can help weigh it up.