Creatine Can Throw Off Our PhenoAge Results: What to Know and How to Fix The Problem

by Nils Osmar

  • © Nils Osmar 2025.  September 10, 2025
  • This post is not intended as, and should not be taken as, medical advice. 
  • See full Medical Disclaimer

Many people today use blood-based calculators such as PhenoAge to estimate their biological age and monitor the effects of lifestyle changes, diet, and supplements. One question that often arises is: “Why does my biological age score change when I take creatine, even if my kidney function is perfect?”

Let’s break down the science — starting with PhenoAge itself, and why it’s such a valuable tool for those hoping to extend their healthy lifespans.

What Is PhenoAge?

PhenoAge is a science-based measure of biological age — an estimate of how well your body is aging compared to the number of years we’ve actually lived (our chronological age). Unlike our age in birthdays, which is based on calendar years, PhenoAge is calculated from a set of several standard blood biomarkers reflecting multiple aspects of health: metabolism, inflammation, immune function, and organ performance.​

How It Works

PhenoAge uses nine common clinical markers:

  • Albumin (liver function, nutrition)
  • Glucose (metabolic health)
  • C-reactive protein (CRP) (inflammation)
  • Lymphocyte count (immune system)
  • Mean cell volume (MCV) (blood cell production)
  • Red cell distribution width (RDW) (oxygen-carrying capacity)
  • White blood cell count (WBC) (infection/inflammation)
  • Creatinine (kidney function)
  • Alkaline phosphatase (ALP) (liver/skeletal metabolism)

After a routine blood test, the results for these markers are entered into a validated statistical model, which was originally developed by scientists Dr. Morgan Levine and Steve Horvath. The model predicts an individual’s mortality risk and biological age based on their body’s current state.

​My Experience

I’ve been using PhenoAge for the past three years to attract changes in my biological age. I get blood tests every 45 to 60 days. When I add a new supplement (such as creatine) I look carefully at my PhenoAge results to see whether it’s having a positive or negative effect on my health and possible longevity.

Why Is PhenoAge Respected?

PhenoAge is highly regarded by researchers and clinicians for several reasons:

  • Predictive Power: It’s been shown in studies to predict healthspan (years lived in good health), disease risk, and even lifespan more accurately than chronological age alone.​
  • Accessibility: PhenoAge uses widely available blood tests, making it affordable and practical compared to some genetic age “clocks.”​
  • Scientific Foundation: The algorithm is built on massive, peer-reviewed population data sets and uses markers routinely checked in medical practice—rather than requiring specialized knowledge or equipment.​

What Are the Benefits?

PhenoAge provides more detailed insight into your body’s aging process, disease risk, and response to lifestyle changes. People with a higher PhenoAge than their chronological age have an increased risk of age-related diseases and earlier mortality, while those with a lower PhenoAge can track the potential positive effects of diet, exercise, and interventions.​

PhenoAge is at the forefront of longevity science, offering a practical, data-driven way of monitoring our actual biological aging and empower us in making meaningful changes. I’ve made changes to my protocol many times over the years after adding a supplement or making a dietary change, and seeing the results in my PhenoAge calculations.

What Are Creatine and Creatinine?

  • Creatine is a popular supplement used to help muscles produce energy during exercise. Your body also makes creatine naturally, and you get small amounts from certain foods.​
  • Creatinine is a waste product formed when creatine breaks down in your muscles. It’s filtered out of your blood by your kidneys, making it a commonly measured marker in blood tests.​

Why Do Blood Tests Include Creatinine?

Doctors measure creatinine levels to assess kidney health. Higher-than-normal creatinine can indicate kidney dysfunction, though other factors can also cause an increase.

“Serum creatinine is a widely used marker in the assessment of renal function. Elevated creatinine levels suggest kidney dysfunction, prompting the need for further investigation. This report describes a case in which the consumption of the bodybuilding supplement creatine… resulted in raised serum creatinine in the absence of true underlying kidney pathology.”
— Williamson & New, Manchester Medical School​

How Does Creatine Supplementation Affect Creatinine?

If you take creatine supplements, your body can produce more creatinine as it metabolizes the extra creatine in your muscles. This increase is expected and does not mean your kidneys are damaged, especially when other kidney and liver markers are normal.​

“Creatine supplements can increase creatinine levels… Ingesting creatine supplements can increase creatinine levels in a metabolic panel, but this elevation does not necessarily indicate kidney dysfunction.”
— National Kidney Foundation, DrOracle AI​

Long-term studies show that recommended creatine doses do not cause kidney damage in healthy adults, even if blood creatinine rises slightly. Creatinine can also go up with high meat intake or greater muscle mass—common among fitness-oriented individuals.​

Creatinine in Biological Age Calculators (PhenoAge)

The PhenoAge calculator uses nine blood-based biomarkers—including creatinine—to estimate biological age. The original algorithm assumes that higher creatinine always implies more biological aging, mainly because it’s often linked to declining kidney function in population studies.

Problem being, if your creatinine rises due to creatine supplementation, this can make your biological age score look “older,” even if your kidneys are healthy. ​

“If you’re tracking your creatinine levels with the goal of optimizing your biological age, it’s important to try to keep creatinine levels relatively low (i.e. around 0.8 mg/dL), and to avoid its age-related increase!”
— Michael Lustgarten PhD​

So What to Do?

  • If your kidney markers (like eGFR, albumin, and others) remain excellent, a rise in creatinine from creatine supplementation is not cause for alarm.
  • You may see a slightly “older” biological age score due to creatinine’s role in calculators like PhenoAge.
  • For this reason, I usually start taking creatine for 48 hours before my blood tests, particularly if I’m testing the bio markers I’ll be entering in the PhenoAge calculator.
  • It’s important to be aware, of course, that high creatinine can sometimes suggest actual kidney problems. So you should always look at your other bio markers to make sure that actual problems aren’t being hidden by the fact that you’re taking creatine.

High Protein Diets

  • One other thing I should mention is that eating a high protein diet can also raise creatinine levels. If this happens, I would look again at your other bio markers before a panicking. High creatinine is a problem with it indicates kidney problems; but this is not always the case.

Educating Doctors

  • One thing that can be a little irksome is that many doctors are unaware of creatine and it’s (benign) effects on our kidney markers. They may see high creatinine levels and freak out.
  • It’s important in my opinion to tell our doctors about the supplements we’re taking, and to educate them about the fact that high creatinine caused by a creatine intake is unlikely to be a problem.
  • I had to quit going to one doctor because he refused to look at the materials that I’d shared with him showing that when creatinine levels are high due to creatine intake, it’s usually not a cause for alarm.
  • My new doctor, who is younger and a little wiser, read the studies I shared with him and agreed to that my high creatinine levels were not a problem.

Summing Up

Creatine supplementation is generally safe for healthy adults and does not damage kidney function—even if it makes your blood creatinine appear elevated. It has anti-aging benefits, so I take it.. Biological age calculators like PhenoAge may misinterpret this elevation as aging, so understand the background and look at your full health profile—not just one number.

References

Acknowledgement

I used Perplexity AI to assist in fact-gathering and content verification for some parts of this article. Its suggestions were carefully reviewed, edited, and modified when necessary. Final responsibility for the content and conclusions rests solely with me

Not medical advice

This article is not intended as, and should not be taken as, medical advice. I’m not advising that people eat any particular diet or take any particular supplement(s), just reporting on what I’m doing. Supplements, like medications and other interventions, can have side effects; I would encourage people to research both possible benefits and side effects before starting on any supplementation regimen, and consult with a medical professional about any issues which might have a medical component.  See full Medical Disclaimer

Other resources

About the Author
Medical Disclaimer

Nils Osmar is the Director of Rekindle School, an independent educational program in Seattle, Washington, established in 2002. He has several websites, exploring questions related to:

• Consciousness in today's Large Language Models

• Life extension and anti-aging

• News, politics, culture and the arts

Unless otherwise indicated, Nils is the author of all of the articles on this site. 

© Nils Osmar 2026.

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