Creatine and Your Body Composition Scan: What Changes

Creatine and Your Body Composition Scan: What Changes and Why

You start creatine, scan a week later, and your lean mass has jumped by a kilogram or more. Is that muscle? Mostly not yet. Creatine pulls water into muscle, and a creatine body composition scan picks up that water as extra fat-free mass. That is true on bioimpedance analysers and on DXA.

That does not make the reading wrong, and it does not mean creatine “only adds water”. It means the first jump and the long-term trend tell you different things. This guide walks through what the research shows happens to body water, lean mass and weight on creatine, and how to time your scans so you can still read your progress honestly.

Why Creatine Changes Body Water

Creatine is stored mainly in skeletal muscle. Supplementing raises the amount held there. In a classic 1996 study of 31 men, taking 20 g a day for six days raised muscle total creatine by about 20%. Taking 3 g a day reached a similar 20% rise more gradually, over 28 days.

Creatine draws water with it into the muscle cell. More creatine in muscle means more water inside cells, and therefore more total body water. Body composition methods read that water as part of your fat-free mass, because fat-free tissue is mostly water.

We are not giving dosing advice here. The amounts above are simply what the researchers used, and they explain why the speed of the change differs between studies.

What the Studies Measured

Two things stand out. First, the change shows up fast: within five to seven days in the loading studies. Second, it appears on every method, including DXA, which many people treat as the reference. No scan is immune.

Is It Just Water? Not Over the Long Run

The early jump is mostly water. Over weeks of training, the picture changes. In the eight-week Ribeiro study, the creatine group gained more muscle, and the ratio of intracellular water to muscle stayed the same. Muscle change and intracellular water change were strongly linked. The authors concluded the muscle gain happened without any change in the ratio of intracellular water to muscle, which argues against pure water retention.

An older nine-week training study reached a similar conclusion. The creatine group gained 2 kg of body mass, but the relative size of the body water compartments stayed constant. The authors attributed the gain to tissue growth with a normal water content, not water retention.

So both statements are true. In week one, the scan mostly sees water. Over months of training, part of the extra lean mass is likely real tissue. Your job is to tell the two apart, and timing is how you do it.

What Happens to Each Number on Your Report

• Weight: often rises in the first week. Deminice saw 1.0 kg in seven days. In women in the Moore study, fluid rose without a weight change, so this varies.
• Total body water and intracellular water: expect a rise. This is the direct effect.
• Fat-free mass, lean body mass and skeletal muscle mass: likely to rise, because these are calculated largely from water on BIA. Read our guide to skeletal muscle mass on InBody for what the number represents.
• Fat mass: creatine is not expected to change fat in a week. A four-week study using underwater weighing found no significant change in percent body fat, while body water rose. Your printed body fat percentage may still dip slightly simply because weight and lean mass went up.
• ECW ratio: watch it rather than assume. Creatine water is mainly intracellular, but the Moore study found extracellular fluid also rose in the luteal phase. Our ECW ratio explainer covers what is normal.

How to Time Your Scans on Creatine

1. Scan before you start. A baseline taken before your first dose is the only clean comparison you will have.
2. Expect a step in the first one to four weeks. Faster with a loading phase, slower with a small daily amount, going by the Hultman study. Do not read that step as muscle gain.
3. Judge muscle over months, not weeks. Once your intake is steady, the water effect should level off too. Changes after that point are more likely to reflect training.
4. Do not start or stop just before a scan. After stopping, muscle creatine in the Hultman study took about 30 days to return to baseline. Expect lean mass and water to drift down over that period.
5. Write it down. Note when you started, stopped or changed your intake, so you or your trainer can explain a jump later.
6. Keep the usual test conditions. Same device, same time of day, no workout or big meal before. Our test preparation guide has the full checklist.
7. Check strength alongside the scan. A rising lean mass with flat strength over months deserves a second look. A handgrip test is a quick cross-check.

Vegetarians, Blood Tests and Safety

Creatine occurs naturally in meat, so vegetarians start with lower stores. A 2020 systematic review of nine studies found supplementation raised muscle creatine in vegetarians, often above omnivore levels, and increased lean tissue mass. The studies had moderate to high risk of bias. For vegetarian Indians, the practical point is that the scan jump may be larger than a meat-eating friend’s.

Creatine can also affect a routine kidney blood test. A 2025 meta-analysis found a small, transient rise in serum creatinine, which the authors attributed to creatine turnover rather than kidney damage, with no significant change in filtration rate. Tell your doctor you take it before any kidney function test, so a raised creatinine is read correctly.

If you have kidney disease, diabetes, are pregnant, are under 18, or take regular medication, talk to your doctor before taking any supplement. Check the product label and the manufacturer’s FSSAI licence details before you buy.

Frequently Asked Questions

Does creatine show up as muscle on an InBody scan?

It shows up as extra fat-free mass. A 2023 study found one week of creatine raised total body water by 2% on an InBody 770 and increased fat-free mass on BIA and DXA. In the first weeks this is mostly water drawn into muscle, not new muscle tissue.

Does creatine affect DXA scans too?

Yes. A 2017 study in trained cyclists concluded that changes in muscle creatine and water alter DXA estimates of lean mass. DXA is not immune, so the same timing rules apply whichever scan you use.

Should I stop creatine before a body composition test?

Not just for one scan. Stopping changes your water level over the following weeks, which makes comparisons harder. It is better to stay consistent and note your intake on your records. If you do stop, expect lean mass and body water readings to drift down over about a month.

Does creatine make you fat?

Studies have not found it raises fat mass. A four-week study using underwater weighing found no significant change in percent body fat. Scale weight can rise because of extra water stored in muscle.

How long does creatine water weight last?

As long as you keep taking it at a steady intake, the extra muscle creatine and water are maintained. In a 1996 study, muscle creatine returned to baseline about 30 days after supplementation stopped.

Will creatine change my ECW ratio?

Possibly a little either way. Most of the extra water is inside cells, but one study in women found extracellular fluid also rose after loading in the luteal phase. Track your own trend under standard conditions rather than assuming a direction.

Get a Clean Baseline Before You Start

The most useful scan is the one you take before the first dose. Find an InBody test centre near you and keep your test conditions the same each time. Coaches and gyms tracking members on supplements can see how InBody works for gyms.

This article is for general education and is not a substitute for medical advice. Talk to your doctor before taking any supplement, especially if you have a kidney condition or take regular medication.

Related reading: lean body mass explained, who should not take an InBody test, and vegetarian muscle building.