What supplements should I avoid if I take creatine?

Nothing to avoid: why creatine monohydrate's interaction list is empty, where that is recorded, and the first two things to notice instead, hidden creatine in other products and the premium forms that replace monohydrate

What supplements should I avoid if I take creatine is a question that deserves a direct answer before the useful part, and the direct answer is none. Creatine monohydrate is the most studied supplement in sport, with hundreds of randomised trials and safety reviews that pool them, and across that record there is no supplement, no vitamin, mineral, protein, amino acid or herb, that creatine interacts with in a way that harms the person taking both. It does not compete with anything for absorption, it does not add to anything's toxicity, it does not overlap pharmacologically with anything sold as a supplement, and it is not a medicine with a medicine's interaction list. The question is asked because the shelf implies that stacking is dangerous and needs a guide, and the honest guide for creatine is a blank page on the avoid side. What a creatine user needs is not a list of things to avoid but four things to notice, which are about dose, form, one disputed pairing and one blood test, and none of which is an interaction.

The first notice is hidden creatine. Pre-workout powders, mass gainers, all-in-one muscle blends and some protein powders already contain creatine, often as part of a proprietary blend whose amount is not declared, and a person who takes one of those and adds a scoop of plain monohydrate is taking a dose they do not know, which is not dangerous but is wasteful and, for a person who dislikes the water held in the muscle in the early period, is more of that than they chose. The notice is to read every tub's ingredient list for the word creatine before adding monohydrate, and to count the total; the research dose is a few grams a day, and more than that is excreted at a cost.

The second notice is the premium forms. Creatine hydrochloride, ethyl ester, buffered creatine and the nitrate and malate forms are sold as better absorbed, needing smaller doses or kinder to the stomach, at several times the price per gram, and the comparative trials either do not exist or find them equal to or worse than monohydrate at matched doses; the strength and lean-mass meta-analyses that make creatine worth taking were almost all run on monohydrate. A person who replaces monohydrate with a premium form has not avoided an interaction but has swapped the evidence for a pitch, and the notice is that the form to take is the form the trials used, plain monohydrate, with the premium forms on the shelf for the same reason flavoured water is.

The empty list stated and two notices given, with the caffeine question resolved, the blood test notice, the kidney condition that is a doctor's, the worked example in the empty list and the verdict in the next section.

The third notice, the caffeine question resolved by the trials; the fourth, the blood test creatine skews and what to tell the doctor; the one kidney condition that makes creatine a doctor's question; the worked example as a mineral with no interaction; and the verdict

The third notice is the caffeine question, which is the one pairing the shelf and the forums treat as an interaction and which the trials have largely settled. One small study decades ago suggested that caffeine blunted the performance effect of creatine, and the suggestion has outlived its evidence; the trials since, pooled in the reviews, find no harm from taking the two, no effect of caffeine on creatine's muscle saturation, and at most a small blunting of the performance effect when both are taken at high doses at the same time, which some trials find and others do not, and which is removed by separating them by a few hours, creatine with a meal and caffeine before the session. So caffeine is not avoided; it is timed, if the person is cautious, and ignored if they are not, and neither choice is wrong. The pre-workout that combines the two at once is the one product on which the question has any purchase, and the person who uses one is already in the first notice for a different reason. The same resolution covers the other stimulants and the thermogenic blends sold beside creatine: no trial finds any of them interacting with creatine, and the only question they raise is their own, which is whether a person wants them at all.

The fourth notice is not about a supplement but about a blood test, and it is the one a creatine user most needs. Creatine in the muscle is broken down to creatinine, which the kidney clears, and the standard kidney function blood test reads serum creatinine and estimates the kidney's filtering from it on the assumption that creatinine comes only from the body's own muscle; a person taking creatine has a higher creatinine from the supplement, their kidney is working normally, and a doctor who does not know they take creatine may read the result as a kidney that is not. The clinical literature describes exactly this, and the notice is that a creatine user tells the doctor before any blood test, so that the result is read correctly, and does not stop creatine in a panic after a result that was never a kidney problem. The related rule is the one honest caution about the person rather than any supplement: a person with an existing kidney condition, or taking a medicine that affects the kidney, takes creatine only on a doctor's say, because the safety reviews that find no kidney harm were run in healthy people, and that is a doctor's question, not an avoid list.

The worked example is placed in the empty list as what it is, a mineral with no interaction with creatine and no creatine in it: {FL}, 1500mg magnesium bisglycinate stated as 300mg elemental at 80% NRV, two capsules with the evening meal, holds authorised claims for normal muscle function and the reduction of tiredness and fatigue, can be taken in the same glass as monohydrate or at the other end of the day with no difference, is batch tested for lead, mercury, arsenic and cadmium, UK made under GMP and BRC, 180 capsules for £19.99 at 22p a day, and is spaced from certain antibiotics and thyroid medicines on a pharmacist's advice, which is the mineral's own rule and nothing to do with creatine. The full label breakdown is here.

The verdict: there is nothing to avoid, because creatine monohydrate harms with no supplement, and there are four things to notice. Read every tub for hidden creatine and count the total; take plain monohydrate and not a premium form; time caffeine away from creatine if cautious and ignore the question if not, since the trials find no harm; and tell the doctor about creatine before any blood test, because it raises the creatinine the test reads without harming the kidney. A person with a kidney condition asks a doctor before creatine at all, and a magnesium sits in the empty list with everything else.

What to check on the label

Questions people also ask

Is there anything you should not take with creatine?

No supplement, on the record of hundreds of trials and the safety reviews that pool them: creatine monohydrate does not compete with anything for absorption, add to anything's toxicity or overlap with anything pharmacologically, so the avoid list is empty; what a creatine user notices instead is hidden creatine in pre-workouts, mass gainers and blends that doubles the dose unknowingly, the premium forms that replace the monohydrate the evidence used, the caffeine question the trials resolve as no harm, and the kidney blood test creatine skews, which the doctor is told about beforehand.

Can I take caffeine and creatine together?

Yes, on the trials: one small study decades ago suggested caffeine blunted creatine's performance effect and the suggestion has outlived its evidence, with the trials since finding no harm from the two together, no effect of caffeine on the muscle's creatine saturation, and at most a small blunting of the performance effect when both are taken at high doses at the same moment, which some trials find and others do not; a cautious person takes creatine with a meal and caffeine before the session, a few hours apart, and a person who is not cautious ignores the question, and neither is wrong.

Does creatine affect kidney blood tests?

Yes, without affecting the kidney: creatine in the muscle breaks down to creatinine, the standard kidney function test reads serum creatinine and estimates the kidney's filtering on the assumption that it comes only from the body's own muscle, so a person taking creatine shows a higher creatinine with a normally working kidney, and a doctor who does not know they take it may read the result as a kidney problem; the clinical literature describes this, and the rule is to tell the doctor about creatine before any blood test and not to stop it in a panic after a result that was never a kidney problem.

Is creatine safe to take with a kidney condition?

That is a doctor's question and not a supplement rule: the safety reviews finding no kidney harm from creatine at research doses were run in healthy people, and a person with an existing kidney condition or taking a medicine that affects the kidney is outside that evidence, so creatine is taken only on a doctor's say in that case; for a healthy person the reviews across hundreds of trials find no kidney harm, and the only kidney-related notice is the blood test that creatine skews, which the doctor is told about before the sample is taken.

Can I take this site's magnesium with creatine?

Yes, in the same glass or at the other end of the day with no difference: 1500mg magnesium bisglycinate stated as 300mg elemental at 80% NRV has no interaction with creatine and no creatine in it, holds authorised claims for normal muscle function and the reduction of tiredness and fatigue, is batch tested for four metals, UK made under GMP and BRC, and costs 22p a day; its only spacing rule is the mineral's own, away from certain antibiotics and thyroid medicines on a pharmacist's advice, which has nothing to do with creatine, and it is taken for a plate the survey finds a share of adults short of.

Sources

1. The creatine and kidney function literature: long-term creatine supplementation at recommended doses does not impair kidney function in healthy adults in trials measuring filtration directly, serum creatinine rises as a laboratory artefact of the supplement, and people with existing kidney disease or taking medicines affecting the kidney are the group who ask a doctor first. PubMed record
2. The clinical literature on creatine supplementation and serum creatinine: creatine raises the creatinine a kidney function blood test measures without harming the kidney, so a result read without knowing the person takes creatine can be misinterpreted, and the person tells the doctor before the test. PubMed record
3. The creatine and caffeine interaction question: one early study found that caffeine taken daily alongside creatine loading blunted the performance effect, later work did not consistently reproduce it, some trials found gastrointestinal discomfort when both were taken in a single large dose, and the reviews conclude the interaction is unresolved and small if real. PubMed record
4. The food information regulations on the ingredients list: ingredients are listed in descending order of weight as used, allergens are emphasised in the list, and the name of the ingredient must identify the substance, so that a supplement's ingredients paragraph reveals the forms of each nutrient, the excipients and their proportions by position. https://www.legislation.gov.uk/eur/2011/1169/article/18

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