Creatine vs Creatinine: What a Creatine Supplement Actually Does — and Why Your Kidney Labs Can Look "Off"

https://youtu.be/qNxc1mc9yA8?si=fhM_PggvdcRdzQJB

By Yoon Hang "John" Kim, MD, MPH — Board-Certified Preventive Medicine Physician specializing in Integrative and Functional Medicine | www.directintegrativecare.com

Abstract

Creatine monohydrate is one of the most extensively studied dietary supplements available, with over three decades of clinical trial data supporting its role in improving strength, lean mass, and high-intensity exercise capacity. Despite this, confusion between creatine (the supplement) and creatinine (its metabolic waste product) continues to cause unnecessary alarm when routine kidney labs come back looking “off.”

This article explains the difference between the two molecules, reviews what the evidence — including 2025–2026 meta-analyses — actually supports regarding muscle performance, cognitive function, and kidney safety, and offers practical guidance on dosing, product selection, and when to involve your physician. Recent data confirm that creatine supplementation modestly raises serum creatinine (approximately 0.13–0.14 mg/dL on average) without corresponding changes in directly measured kidney filtration, reinforcing that this is a lab artifact rather than evidence of kidney injury in healthy individuals.

The goal is simple: help you understand what creatine does, what it does not do, and how to have a smarter conversation with your clinician about what your labs actually mean.

Patients ask about creatine more often now than they did five years ago. It used to live almost entirely in the gym conversation. It now shows up in conversations about aging muscle, brain fog after poor sleep, plant-based diets, and "my creatinine came back high and my doctor is worried."

That last sentence is why this article exists.

Creatine and creatinine sound like the same molecule with a typo. They are not. Confusing them leads people to stop a useful supplement — or, worse, to ignore a real kidney problem because "it's just the creatine." Both mistakes are avoidable.

This is educational, not a prescription. If you have kidney disease, take medications that affect the kidneys, or you are pregnant or breastfeeding, talk with your own clinician before you start anything.

Creatine and Creatinine Are Related — They Are Not Interchangeable

Creatine is a compound your body makes from three amino acids: arginine, glycine, and methionine. About 95% of body creatine is stored in skeletal muscle, with roughly two-thirds present as phosphocreatine. When you need a fast burst of energy — a heavy lift, a sprint, standing up quickly as you get older — phosphocreatine donates a phosphate group to regenerate ATP.

Your liver, kidneys, and pancreas make about 1 gram a day. A typical omnivorous diet adds another 1–2 grams from meat and fish. Muscle stores sit about 60–80% full on diet alone. Supplementation can raise those stores another 20–40%.

Creatinine is the waste product. Every day, roughly 1–2% of your muscle creatine pool spontaneously breaks down into creatinine. The kidneys filter it. That is why serum creatinine (and the eGFR calculated from it) became a routine kidney marker.

A simple way to remember it:

• Creatine is the fuel.

• Creatinine is the exhaust.

More fuel in the tank means a little more exhaust. That does not automatically mean the engine is failing.

What the Evidence Actually Supports

Creatine monohydrate is one of the most studied dietary supplements we have — hundreds of trials over three decades. The International Society of Sports Nutrition has called it the most effective ergogenic nutritional supplement currently available for increasing high-intensity exercise capacity and lean mass during training.

What holds up

Strength and lean mass when you train.

Combined with resistance training, creatine reliably improves strength and adds lean mass — often around 1 kg of additional lean mass on average, with larger gains in some studies — over 8–12 weeks in study settings. It does not replace training. It helps you do a little more work in the sessions you already do.

Aging muscle (sarcopenia).

We lose muscle with age. That loss is not cosmetic. It affects balance, blood sugar handling, recovery from illness, and independence. Creatine plus protein plus actual strength work is one of the more practical stacks we have for older adults.

People who eat little or no animal protein.

Vegetarians and vegans start with lower muscle creatine stores. They frequently see substantial increases in tissue creatine after supplementation, although evidence that their performance response is always greater than omnivores is mixed. In practice, many notice a real difference.

Brain energy under stress.

The brain uses creatine too. The performance data is strongest for muscle. The cognitive data is newer and smaller, but directionally interesting: a 2024 meta-analysis found modest benefits for memory and some processing measures, particularly under sleep deprivation or metabolic stress. Preliminary adjunctive research in depression exists, but the clinical benefit remains very uncertain. I treat the cognitive angle as promising, not settled.

Postmenopausal women.

A 2026 meta-analysis found a small increase in lean mass (roughly 0.37 kg) and improved leg-press strength when creatine — especially at doses of 5 grams per day or more — accompanied resistance training. Bone-density benefit was not demonstrated overall, but the muscle and strength conversation overlaps meaningfully with the bone conversation in this population. Evidence is growing, not finished.

What does not hold up

• Creatine is not a steroid.

• Creatine is not a fat-gain drug. Early scale weight is mostly intramuscular water.

• Fancy forms (ethyl ester, "buffered," many patented variants) have not beaten plain creatine monohydrate in head-to-head work. Some — creatine ethyl ester in particular — convert to creatinine faster and actually perform worse. Pay for purity and third-party testing, not for a new molecule name.

Does Creatine Damage the Kidneys?

In healthy people, at usual doses, the best available evidence says no.

What creatine does do is raise the lab number we use as a kidney proxy. Creatine can modestly increase serum creatinine because more creatine is available for conversion to creatinine. Recent meta-analyses — including two published in 2026 — found an average serum creatinine increase of about 0.13–0.14 mg/dL. Creatinine-based eGFR may therefore appear lower even when true kidney filtration has not changed. Crucially, when researchers measured filtration directly using creatinine-independent methods (such as Cr-EDTA clearance), they found no change. That strongly suggests a measurement artifact, not nephron injury.

Side-effect rates in pooled trial data look similar to placebo; the most common complaints are gastrointestinal discomfort if the dose is dumped in all at once.

One nuance worth noting: long-term randomized data beyond approximately one year are much thinner than the short- and medium-term evidence. So I will not say renal safety has been proved indefinitely in every population. What I will say is that the current evidence, across a large number of studies, has not shown a signal of kidney damage in healthy adults using recommended doses.

The caveat is real and I do not wave it away:

• Known chronic kidney disease

• eGFR already reduced

• Nephrotoxic medications

• Unexplained rising creatinine before anyone started creatine

• Pregnancy and lactation (not enough safety data)

Those are "talk to your physician first" situations, not internet-protocol situations. If you are already on creatine and a routine panel looks worse, tell the person reading the labs. Ask whether cystatin C — a kidney marker that is not generated from creatine metabolism and is less dependent on muscle mass — would clarify the picture. Combining creatinine and cystatin C can sometimes give a more informative estimate than relying on creatinine alone. Temporarily stopping creatine and repeating testing after an appropriate interval can also sometimes clarify the picture.

How I Think About Dosing in Practice

There are two honest ways to saturate muscle stores.

Daily low dose (what most people should do):

3–5 grams of creatine monohydrate every day. Saturation takes three to four weeks. Fewer GI issues. No drama.

Optional loading:

About 20 grams a day, split into 4 doses of roughly 5 grams each, for 5–7 days, then 3–5 grams daily. Faster saturation. More water retention and more GI complaints. Not required.

I generally skip loading unless someone has a time-sensitive training block and tolerates split doses. Consistency beats cleverness.

Practical notes that matter more than timing debates

• Take it with food if your stomach is sensitive.

• Maintain normal hydration. Creatine can increase intracellular water, especially early in supplementation, but controlled studies do not show that it causes dehydration.

• Powder is cheaper and fine. Capsules are convenience, not magic.

• Look for creatine monohydrate, ideally Creapure or another batch that is third-party tested (NSF, Informed Sport, USP). The risk in this category is usually a dirty product, not the molecule.

• You do not need to "cycle" it if you are healthy and the dose is ordinary.

Who Is a Reasonable Candidate — and Who Is Not

Reasonable to discuss:

• People who lift or do repeated high-intensity work

• Adults over 50 trying to keep muscle

• Vegetarians and vegans

• Patients whose fatigue picture includes low training capacity and who already have a training plan

• Some women in peri- and postmenopause, where muscle and bone conversations overlap

Pause and get medical input first:

• Established kidney disease

• Unexplained abnormal creatinine or eGFR

• Heart failure with tight fluid management

• Adolescents should not self-experiment; use should occur with appropriate parental and professional supervision. The ISSN considers supervised use acceptable in appropriately trained young athletes, but that is different from a teenager ordering it online.

• Pregnancy and breastfeeding — human supplementation safety data remain insufficient to recommend routine use

Creatine is not a treatment for fibromyalgia, MCAS, autoimmune disease, or cancer. In my practice those conditions have their own frameworks. If someone in that group also wants to protect muscle while they train, we talk about labs, hydration, and the creatinine-lab artifact before they start — not after a panicked portal message.

How This Fits a Functional Medicine Visit

A supplement is never the first question I ask. The first questions are still the boring ones that change outcomes: protein intake, resistance training two or three days a week, sleep, hydration, and whether the person can actually recover from the work they are doing.

If those pieces are in place, creatine monohydrate is one of the few supplements with a risk-benefit ratio I am comfortable discussing in clinic. If those pieces are missing, creatine will not rescue the plan.

If you are a patient of Yoon Hang Kim MD and you start creatine, put it on your supplement list and tell me before the next lab draw. That single sentence prevents a lot of unnecessary alarm.

Frequently Asked Questions About Creatine

Is creatinine a supplement?

No. Creatinine is a waste product. The supplement is creatine.

Will creatine make my creatinine high?

It can raise the number modestly. That is not the same as kidney failure. Context and, when needed, a second marker like cystatin C matter.

What form of creatine should I buy?

Creatine monohydrate. Micronized dissolves more easily. Everything else needs a better reason than marketing.

Do I need a loading phase?

No. Helpful if you want saturation in a week. Unnecessary if you can wait a month.

Can I take creatine with LDN or other medications?

No specific interaction between creatine and low-dose naltrexone has been established in the published literature, although formal interaction data are limited. The practical issue is the creatinine lab, not a drug-drug clash. Medication lists still belong in the conversation with your prescriber.

Does creatine cause hair loss?

An older small study raised concern about a DHT shift in a group of rugby players. However, a 2025 randomized trial measured DHT and actual hair-follicle and hair-density outcomes after 12 weeks of 5 grams per day of creatine and found no significant differences from placebo. Current evidence does not support creatine causing hair loss.

Summary

What creatine is: A naturally occurring compound stored primarily in skeletal muscle that helps regenerate ATP during short, high-intensity efforts. Your body makes about 1 gram per day; diet adds 1–2 grams; supplementation can raise muscle stores by 20–40%.

What the evidence supports: Creatine monohydrate, at 3–5 grams daily, reliably improves strength and lean mass when combined with resistance training. Benefits extend to older adults fighting sarcopenia, vegetarians and vegans with lower baseline stores, and postmenopausal women. Cognitive benefits under metabolic stress are promising but not yet settled.

What it does to your labs: Creatine raises serum creatinine by roughly 0.13–0.14 mg/dL on average, which can make eGFR look lower. Two 2026 meta-analyses confirmed this is a measurement artifact — directly measured kidney filtration does not change. This is not kidney damage. It is more exhaust from a fuller tank.

What it does not do: It is not a steroid. It does not cause dehydration. It does not cause hair loss (a 2025 randomized trial found no effect on DHT or hair density). Fancy branded forms have not outperformed plain creatine monohydrate.

Who should pause: Anyone with established kidney disease, unexplained abnormal creatinine, heart failure with tight fluid management, unsupervised adolescents, or women who are pregnant or breastfeeding should get medical guidance before starting.

The bottom line: Creatine monohydrate is one of the best-supported, lowest-risk, and least expensive supplements available for healthy adults who train. If your creatinine rose after you started it, do not panic and do not ignore it. Bring the bottle, the dose, and the timeline to the clinician who ordered the labs. That conversation is the whole point.

The Honest Bottom Line

Creatine monohydrate is not a miracle, and it is not a menace. For healthy adults who train, eat enough protein, and understand what their labs mean, it is one of the better-supported, inexpensive tools we have for muscle and high-intensity work. For people with real kidney disease, it is a medical decision, not a cart-checkout decision.

If your creatinine rose after you started creatine, do not panic and do not ignore it. Bring the bottle, the dose, and the timeline to the clinician who ordered the labs.

If you want help sorting whether creatine belongs in your plan — next to the rest of your history, medications, and labs — that is the kind of conversation we have at Yoon Hang Kim MD.

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Yoon Hang "John" Kim, MD, MPH, FAAMA, is a board-certified preventive medicine physician specializing in integrative and functional medicine. He is an IFM Scholar, a graduate of the University of Arizona Integrative Medicine Fellowship under Dr. Andrew Weil, and provides telemedicine care through Yoon Hang Kim MD to patients in Iowa, Illinois, Missouri, Georgia, Florida, and Texas.

This article is for educational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before starting or changing any supplement or treatment.