Creatine side effects: what actually happens

Creatine has one of the longest safety records of anything sold in a supplement shop. The international position stand on it reports up to 30 grams a day for five years as safe and well tolerated in healthy individuals, which is six times a normal serving for five years. That is a far stronger dataset than most things people take without a second thought.

Two genuine effects are worth understanding, one practical issue is worth planning around, and three widely repeated claims do not hold up. None of this changes what creatine is or what it does; it is the other half of the same page. In order: water in muscle is real, stomach discomfort at high or poorly dissolved doses is real, the blood test complication is real and catches people out, and hair loss, kidney damage in healthy people and cramping are not supported.

Creatine is not suitable for people with kidney disease. If you take prescribed medication or are managing a health condition, talk to your doctor before starting.

Creatine is stored inside muscle cells, and it brings water with it. That is not a flaw in the design, it is how the cell holds the stuff. A supplement that raised muscle creatine without raising intracellular water would be doing something biologically odd.

The best measurement of how much comes from a 2023 trial that deliberately took resistance training out of the picture. One week of creatine at 0.3 grams per kilogram of bodyweight raised total body water by about two per cent, which showed up on body scans as 1.1 to 1.9kg of extra fat-free mass.

Where the water sits matters more than how much of it there is. This is water drawn into the muscle cell, not fluid held under the skin, so it does not produce the puffy, soft look people picture when they hear the word. If you are watching a number on a bathroom scale, it will move. If you are watching a mirror, generally it will not.

It also settles. The rise happens while your stores are filling and then stops, because the stores are full and there is nothing left to fill.

Almost every argument about creatine and bloating is two people discussing different problems, so it is worth separating them.

The scale version is what we have just covered. A kilo or two appearing in the first weeks, no change in how clothes fit, and no discomfort attached to it. That is water in muscle and it is the mechanism working.

The stomach version is an actual feeling: fullness, heaviness, occasionally cramping or looser stools in the first few days. That is a real experience, it has nothing to do with water in muscle, and it has two causes that are both largely within your control.

Cause one is the size of the dose. Taking 20 grams a day during a loading phase means four or five grams of powder hitting your gut at once, several times a day. Gastrointestinal upset during loading is the most commonly reported complaint in the entire creatine literature, and it mostly disappears when the loading phase does.

Cause two is undissolved powder. Raw creatine monohydrate is not very soluble. Left coarse, a good portion of it never actually dissolves, and what you are swallowing is a suspension of gritty particles rather than a solution. That sits heavier than dissolved creatine does, and it is the specific problem that finer processing addresses.

Being precise about that, because the category is not: complete dissolution does not stop creatine drawing water into muscle and nothing does. What it changes is whether you swallow a glass of grit. Those are different complaints that got merged into one word.

Five things, in rough order of how much difference they make.

• Skip the loading phase. It is optional. Loading gets your stores full in about a week instead of three to four, and the destination is identical either way. If your stomach is the reason you are reading this, do not load.
• Dissolve it properly, and drink it while it is dissolved. Warmer water helps. Stirring properly helps. Powder sitting in the bottom of the glass is both a smaller dose than you think and the part most likely to upset you.
• Split a larger dose. If your bodyweight-adjusted serving is 8 or 10 grams, taking it in two halves is easier on the gut than taking it in one hit.
• Take it with a meal. Not required, and a small real advantage rather than a rule.
• Drink water. Standing advice on the pack, and sensible whether or not you notice anything.

This is the most practically useful thing on this page, particularly if you are over fifty and have annual bloods done.

Routine kidney screening does not measure your kidneys directly. It measures creatinine, a waste product your body makes as it uses creatine, and then estimates your kidney function from that number. More creatine in the system means more creatinine in the blood, whether or not anything has changed in your kidneys, and the estimate goes down accordingly.

The practical consequence is what matters. A result like that can lead to repeat testing, a referral, or a period of worry, none of which you needed. A single sentence to your doctor avoids all of it. Say you take creatine daily, and say it before the blood is drawn rather than after the result comes back.

None of this changes the standing exclusion. Creatine is not suitable for people with kidney disease, and this page is not a reason for anyone with an existing kidney condition to reconsider.

This is the creatine question with the widest gap between what people believe and what has been tested, and the gap closed recently enough that most of what you will read online has not caught up.

Where it started. In 2009, researchers gave 20 college-aged rugby players in South Africa creatine at 25 grams a day for a week, then 5 grams a day for a fortnight. DHT, a hormone associated with male pattern baldness, rose by around 41 per cent, from 0.98 to 1.26 nmol per litre. Two details usually get dropped when that study is quoted: both of those values sit inside the normal reference range, and the study did not measure hair at all. It measured a hormone in twenty young men and speculated about the rest.

For sixteen years, that was the entire evidence base.

What happened in 2025. A randomised controlled trial set out to test the actual question. Forty-five resistance-trained men aged 18 to 40 were randomised to 5 grams a day of creatine monohydrate or a matched placebo for twelve weeks, with hormones and hair follicle health both measured directly.

The limitation, because it is a real one. That trial ran in resistance-trained men aged 18 to 40. It does not directly tell you anything about women, or about anyone over forty, and one twelve-week trial is not the end of a literature. The research that has been done in women is a separate body of work and it is largely about muscle, bone and memory rather than hormones. What it does do is replace a hormone measurement in twenty rugby players with a direct measurement of the thing people were actually worried about, which is a considerable improvement on where this question sat a year ago.

Cramping and dehydration. The international position stand that reviewed this literature concluded creatine does not cause either. The belief is a holdover from early speculation: creatine pulls water into muscle, so people reasoned it must pull water from somewhere else. It does not work out that way when it is measured. If cramp is the thing you actually want solved, magnesium is the more relevant conversation. Drink water anyway, for the ordinary reasons.

Stopping. There is no withdrawal, no rebound and nothing to taper. Muscle stores drift back to baseline over roughly four to six weeks and your body carries on making its own gram a day as it always has. Cycling on and off is also unnecessary, and the trials that ran longest gave creatine continuously for months or a full year.

Loading is not compulsory. Worth repeating in this context, because loading is the source of most of the discomfort attributed to creatine generally.

Short list, and it is on the pack for a reason.

Anyone with kidney disease. Not a caution, an exclusion.

Anyone taking prescribed medication or managing a health condition, without talking to their doctor first. That is not a disclaimer being padded out; the blood test issue above is a concrete example of why your doctor should know.

Anyone pregnant or breastfeeding, without medical advice.

Beyond that, and assuming a normal serving, creatine is one of the better-characterised things you can take. We are not going to invent extra contraindications to sound cautious.

Of everything on this page, exactly one item is a formulation problem rather than a physiology one, and it is the grit. Here is our co-founder Andrew on it.

What that fixes is the swallowing of undissolved powder. It does not stop creatine drawing water into muscle, because nothing does and nothing should. The rest of what separates one tub from another is a longer and less interesting list than the packaging suggests.