Supplement Label Glossary: Creatine & Magnesium Terms

Supplement labels use a lot of words that sound technical and mean something quite specific. This glossary explains the ones you'll meet on creatine and magnesium products, and on this site, in plain English. Each entry links to the guide that goes deeper.

Reading any supplement label

Supplement Facts panel

The box on the back or side of a US supplement, usually in black and white. It's the part of the label that has rules behind it: it has to list the serving size and the amount of each active ingredient per serving. When the front of the bottle and the panel disagree, trust the panel. Our magnesium glycinate guide has an example with the important line marked.

Serving size

How much of the product all the amounts on the panel refer to: one scoop, two capsules, 5 g of powder. Check it before you compare products. A bottle that says 400 mg per serving with a two-capsule serving gives you 200 mg per capsule.

% Daily Value (%DV)

The amount per serving as a percentage of a reference daily amount the FDA sets for food labels. For magnesium, the Daily Value is 420 mg. It's a labeling yardstick, not a personal target, and it isn't the same as the safe upper limit. Creatine has no Daily Value, so you'll see a symbol (usually †) instead.

Other ingredients

Everything in the product that isn't an active ingredient: the capsule shell, flow agents, flavors, sweeteners, fillers. It's also where a hidden second form can show up. Magnesium oxide in the other ingredients of a glycinate product means it's buffered.

Proprietary blend

A named mix of ingredients where the label gives the total weight of the blend but not how much of each ingredient is in it. It's legal, and it makes it impossible to know whether you're getting a useful dose of anything. We don't recommend products built around one.

Magnesium terms

Elemental magnesium

The weight of the magnesium itself, as opposed to the whole compound it's bound to. Magnesium glycinate is only about 14% magnesium by weight, so 1,000 mg of the compound gives you about 140 mg of elemental magnesium. This is the number to dose by, and it's the one on the Supplement Facts panel. Our magnesium label checker converts any form.

Chelated, chelate

A chelated mineral is held by an amino acid, often in a ring-like structure. In magnesium glycinate, the magnesium is chelated by glycine. Chelated forms tend to be gentle on the stomach. "Chelated" on its own doesn't tell you which amino acid, or how much magnesium you're getting.

Glycinate, bisglycinate

Magnesium bound to the amino acid glycine. "Bisglycinate" means each magnesium is attached to two glycine molecules, which is how glycinate supplements are made, so for buying purposes the two words mean the same thing. See what magnesium glycinate is.

Fully reacted

A claim that all the magnesium in the product has been bound to its partner, with no leftover unreacted magnesium oxide mixed in. Look for it, or "100% chelated", if you want pure glycinate.

Buffered

On a magnesium label, buffered usually means the product mixes a chelated form like glycinate with a cheaper, more concentrated form, typically magnesium oxide. That fits more magnesium into each capsule but makes stomach upset more likely. On a creatine label, "buffered" means something different: see buffered creatine.

Magnesium oxide

The most concentrated common form, about 60% magnesium by weight, and the cheapest. It's also poorly absorbed and the form most likely to cause diarrhea. Useful as a laxative or antacid, less so as a daily supplement. See glycinate vs citrate and the other forms.

Magnesium citrate

Magnesium bound to citric acid, about 16% magnesium by weight. Well absorbed and inexpensive, with a mild laxative effect at higher doses. Some people take it for exactly that reason.

Magnesium L-threonate

A newer form, sold for memory and focus, with only about 7% magnesium by weight. It's the most expensive common form, and you need several capsules to get a meaningful dose. The evidence for its brain claims is limited.

RDA (Recommended Dietary Allowance)

The daily amount of a nutrient that meets the needs of almost all healthy people, from food and supplements combined. For adults, magnesium's RDA is 310 to 320 mg for women and 400 to 420 mg for men (NIH).

Upper limit (UL)

The most you can take daily without a likely risk of side effects. For magnesium, the US upper limit is 350 mg a day from supplements, not counting what's in food. Above that, diarrhea and cramping become more likely.

Creatine terms

Creatine monohydrate

Creatine bound to one molecule of water. It's the form used in nearly all the research, the cheapest, and about 88% creatine by weight. No newer form has beaten it in head-to-head trials. See the best form of creatine.

Micronized

Creatine monohydrate ground into finer particles so it dissolves and mixes more easily. It's the same creatine, so it works the same; it just leaves less grit at the bottom of the glass. It usually costs little or nothing extra.

Creapure

A brand of creatine monohydrate made by AlzChem in Germany, known for strict purity testing. Many supplement brands buy it and print the Creapure logo on their tubs. It's still monohydrate, and it was used in a lot of the research.

Creatine HCl

Creatine bound to hydrochloric acid. It dissolves far better in water than monohydrate, but it contains less creatine per gram (about 78%), costs two to three times as much, and hasn't worked better in head-to-head trials.

Buffered creatine

Creatine sold with an alkaline buffer, often under the name Kre-Alkalyn, on the claim that it breaks down less in the stomach. A controlled trial found it worked no better than plain monohydrate, even at lower doses.

Loading phase

Taking a higher dose, usually about 20 g a day split into four doses, for 5 to 7 days to fill your muscles with creatine quickly. It's optional: 3 to 5 g a day gets you to the same place in three to four weeks. Our creatine calculator works out both plans.

Maintenance dose

The daily amount that keeps your muscle creatine topped up once it's full: 3 to 5 g for most people. If you skip the loading phase, this is simply your daily dose from day one.

Phosphocreatine

The form most of the creatine in your muscles is stored in, with a phosphate group attached. It rebuilds ATP, the molecule muscles run on, during the first few seconds of hard effort. Taking creatine raises your phosphocreatine stores. See what creatine is.

Creatinine

The waste product left when your body uses creatine. Doctors measure creatinine in your blood to estimate kidney function, and taking creatine raises it slightly. That can make a routine blood test look worse than your kidneys really are, so tell your doctor you take creatine. See is creatine safe?

Testing and quality

Third-party tested

The product has been checked by an independent lab or certification program, not just the company that makes it. The phrase on its own means little. What matters is which program did the testing, and whether you can find the product in its public database.

NSF Certified for Sport

A certification from NSF, an independent testing organization. It checks that the product contains what the label says, screens for contaminants and for substances banned in sport, and audits the factory. Certified products are listed in a searchable database on NSF's website.

Informed Sport

A certification program that tests every batch of a product for substances banned in sport before it's released for sale. Products and batch numbers can be looked up on its website. Its sister program, Informed Choice, tests samples on a regular schedule rather than every batch.

USP Verified

A mark from USP, the organization that sets standards for medicines in the US. It confirms the product contains the listed ingredients in the stated amounts, isn't contaminated with harmful levels of things like heavy metals, and will break down properly in the body. It doesn't screen for substances banned in sport.

GMP, "made in a GMP facility"

Good Manufacturing Practice: the manufacturing rules the FDA requires all US supplement makers to follow. "Made in an NSF-registered facility" or "GMP certified" means the factory was audited. It doesn't mean the product inside the tub was tested.

Research terms

Randomized controlled trial

A study where people are randomly assigned to take the supplement or a comparison, usually a placebo. Randomizing means the two groups start out alike, so any difference at the end is likely down to the supplement. It's the strongest kind of single study for questions like "does this work?".

Placebo

A dummy version of the treatment, such as a capsule with no active ingredient, given to the comparison group. People often feel better on a placebo, which is why a supplement needs to beat it, not just show improvement.

Systematic review, meta-analysis

A systematic review gathers all the studies on a question using set rules. A meta-analysis goes a step further and combines their results into one overall estimate. Both are usually more reliable than any single study, as long as the studies that went into them were good.

Statistically significant

A result unlikely to be down to chance alone. It doesn't mean the effect is big or that you'd notice it. The 2025 magnesium sleep trial was statistically significant, but the improvement was modest. That's why our guides describe how large an effect was, not just whether it was "significant".

Evidence grade

Our shorthand for how strong the research behind a claim is: Good (several controlled trials agree), Mixed (they disagree), Early (one or two small trials) or Weak (little support). How we grade evidence.

Questions people ask

What does elemental magnesium mean?

The weight of the magnesium itself, not the whole compound it's bound to. It's the number on the Supplement Facts panel, and the one to dose by.

Is micronized creatine better?

It's the same creatine monohydrate ground finer, so it mixes more easily. It works the same as regular monohydrate.

Does 'made in an NSF-registered facility' mean the product is tested?

No. It means the factory was audited for manufacturing standards. Product testing is a separate certification, such as NSF Certified for Sport.

Written by Tom D

Tom has trained in the gym for years and has taken 5 g of creatine every day for about a decade, with magnesium on and off for most of the year. Reading the research behind supplements started as a hobby; this site is where he writes it up. He isn't a doctor or dietitian, so every claim links to the study behind it.

Sources

We link to the original study wherever we can. Read how we grade evidence and choose products.