Creatine vs Creatinine: The Key Differences

Man pours powder from red bottle

Creatine and creatinine, two terms often used interchangeably in discussions about fitness and health, play distinct roles in the body.

This article aims to shed light on the differences between creatine and creatinine, address concerns regarding the impact of creatine supplementation on creatinine levels, and provide guidance on the safety of creatine intake.

Creatine, synthesized in the liver and obtained from protein-rich foods, serves as an energy source for muscles during intense physical activities. On the other hand, creatinine, a byproduct of creatine breakdown in muscles, is eliminated through the kidneys as waste.

Quick Summary

  • Creatine is a natural compound produced in the liver and obtained from protein-rich foods. It serves a crucial role in supplying energy to muscles during intense physical activities.
  • Creatinine is a byproduct of creatine breakdown in muscles, eventually excreted through the kidneys.
  • While creatine is generally safe for those with healthy kidneys, excessive use may lead to an increase in serum creatinine levels, prompting concerns during routine kidney function tests.

Are Creatine and Creatinine the Same?

Creatine is a naturally produced compound in the liver and is also acquired through dietary sources, particularly protein-rich foods such as red meat and fish.

Creatine plays a vital role in providing energy to muscles, especially during intense physical activities. Creatine consists of three amino acids: glycine, arginine, and methionine.

In contrast, creatinine is a byproduct that results from the breakdown of creatine within the muscles. It is eventually eliminated from the body through the kidneys as a waste product.

Creatine to Creatinine Conversion: Creatine Metabolism

Creatine to creatinine conversion is one step during creatine metabolism. Creatine metabolism refers to the biochemical processes that involve the production, utilization, and conversion of creatine in the body. 

Scientific equation for Creatine

Creatine synthesis

Creatine is primarily synthesized in the liver, but smaller amounts are also produced in the kidneys and pancreas. The synthesis involves three amino acids: glycine, arginine, and methionine.

Creatine Storage in Skeletal Muscle

After synthesis or dietary intake, creatine is transported through the bloodstream to skeletal muscles. In the muscles, creatine is stored in the form of creatine phosphate.

Energy Transfer

During periods of high energy demand, such as muscle contraction, creatine phosphate donates its phosphate group to adenosine diphosphate (ADP), converting it back to adenosine triphosphate (ATP). ATP is a crucial molecule for storing and transferring energy within cells.

Conversion to Creatinine

Over time, creatine is non-enzymatically dehydrated and converted into creatinine.

Elimination

Creatinine is mainly filtered by the kidneys in the glomerulus. A small proportion of creatinine is actively secreted through tubular secretion. There is minimal reabsorption in the renal tubules.

Clinical Significance

Creatinine levels in the blood and urine are important indicators of kidney function. Abnormal creatinine levels may suggest impaired renal function.

Creatine Supplementation

Creatine supplements are widely used in the fitness and athletic communities to enhance performance, as they are believed to improve the ability of muscles to resynthesize ATP, leading to benefits such as increased strength and shortened recovery times.

Case Report: Creatine Supplements and Serum Creatinine Levels

Recent studies have raised concerns about the potential impact of creatine supplements on serum creatinine levels, particularly in individuals without underlying kidney pathology. 

While creatine is generally safe for those with healthy kidneys, excessive use may lead to an increase in serum creatinine levels, prompting concerns during routine kidney function tests.

White Creatine powder with yellow scoop on pink surface

Is Creatine Safe to Take Every Day?

Long-term and short-term scientific studies have consistently shown no adverse effects of creatine supplementation on kidney function in people with healthy kidneys.  

For individuals with healthy kidneys, creatine supplementation is generally considered safe when used within recommended dosages.  However, maintaining proper hydration and monitoring creatinine levels regularly is crucial, especially if incorporating creatine supplements into your daily routine.

What Does the Creatinine Test Measure?

Creatinine tests are commonly used to evaluate kidney function by measuring serum creatinine levels. 

Creatine supplement doses ≤5 g/day in healthy adults are unlikely to raise creatinine levels significantly, but higher doses can increase creatinine levels leading to a false positive result which can be misinterpreted as a sign of kidney damage.

In a laboratory setting, creatinine levels are often used to calculate the glomerular filtration rate (GFR), a key indicator of kidney function. 

However, GFR can be affected by various factors, and relying solely on serum creatinine concentration may not provide a complete picture. For instance, in bodybuilders, muscle mass can potentially underestimate GFR, so caution is advised.

Alternative Tests

To determine if elevated serum creatinine levels result from decreased kidney clearance, tests like the creatinine clearance test or measuring cystatin C can be used. 

Cystatin C offers a more accurate estimate of GFR as it is less affected by diet or muscle mass.

In a study involving 18 athletes using a randomized, double-blind, placebo-controlled design, the impact of creatine intake (10 g/day for 3 months compared to a placebo) on cystatin C levels was investigated. The researchers found that creatine did not cause any significant changes in the estimated GFR when assessed through cystatin C; in fact, cystatin C levels decreased.

Pair of kidneys held between hands

Pro Tip: Test Before Supplementing

Taking a Creatine Test

Before incorporating creatine into your routine, it’s advisable to undergo creatinine level testing. This allows you to establish a baseline and assess your kidney function. If you’re already using creatine but intend to undergo creatinine testing, discontinue supplementation three weeks before the test to avoid potential false positives.

Receiving Test Results

Upon receiving creatinine test results, it is crucial to interpret them in consultation with a healthcare professional. While elevated creatinine levels may warrant further investigation, it is essential to consider various factors before attributing them solely to creatine supplementation.

What Can Increase Creatinine Levels?

Several factors can contribute to elevated creatinine levels aside from creatine supplementation. Some of these factors include:

  • Kidney Dysfunction: Impaired kidney function is a common cause of elevated creatinine levels. Conditions such as chronic kidney disease (CKD), glomerulonephritis, and kidney infections can affect the kidneys’ ability to filter creatinine. 
  • Dehydration: Reduced fluid intake or dehydration can lead to higher concentrations of creatinine in the blood. Adequate hydration is essential for maintaining normal creatinine levels.
  • Certain Medications: Some medications, such as nonsteroidal anti-inflammatory drugs (NSAIDs), certain antibiotics, and certain diuretics can influence creatinine levels.
  • Muscle Injury or Damage: Conditions that cause muscle injury or breakdown, such as rhabdomyolysis or severe muscle trauma, can elevate creatinine levels. This is because creatinine is a byproduct of muscle metabolism.
  • High-Protein Diet: Consuming a diet high in protein, especially red meat, can lead to increased creatinine levels. This is because creatinine is a byproduct of the breakdown of creatine, which is found in muscle tissue and obtained through protein-rich foods.
  • Intense Exercise: Strenuous physical activity, particularly activities that involve significant muscle usage, can temporarily elevate creatinine levels. This is often seen in athletes or individuals engaging in intense training.
Scoop with mysterious white powder

Takeaway

In conclusion, understanding the key differences between creatine and creatinine is crucial for individuals interested in fitness and health. While creatine serves as a vital energy source for muscles during intense activities, creatinine is a byproduct eliminated through the kidneys. 

Creatine supplementation is generally safe for those with healthy kidneys, but excessive use may raise serum creatinine levels, prompting caution during kidney function tests. 

Before starting creatine supplementation, undergoing creatinine level testing is advisable, and interpreting results with a healthcare professional is crucial. Various factors, such as kidney function, dehydration, medications, muscle injury, high-protein diets, and intense exercise, can contribute to elevated creatinine levels, emphasizing the need for a comprehensive approach to health and fitness.

Frequently Asked Questions

Is creatine the same as creatinine?

No, creatine and creatinine are not the same. Creatine is a compound vital for energy transfer in muscles, while creatinine is a waste product resulting from creatine breakdown in muscles when present in blood and urine.

Will creatine raise my creatinine levels?

While creatine can influence creatinine levels, moderate use is generally safe for individuals with healthy kidneys.

Is creatine OK for kidneys?

In moderation, creatine is considered safe for individuals with healthy kidneys. However, those with pre-existing kidney conditions should consult a healthcare professional before using creatine supplements.

What level of creatinine is alarming?

The normal range for serum creatinine levels in men with healthy kidneys is roughly 0.6 to 1.2 mg/dL, while for women, it’s between 0.5 to 1.1 mg/dL. Elevated creatinine levels beyond this range are associated with a decline in glomerular filtration rate (GFR) and signify renal dysfunction.

References

Joanna Tsintaris | Registered Dietitian | MS Nutrition & Dietetics

Joanna Tsintaris | Registered Dietitian | MS Nutrition & Dietetics

Joanna is a registered Dietitian in the UK and Biomedical Science graduate with first class MSc in Nutrition and Dietetics. She is also the founder of Nourish (RD)—an online health and nutrition clinic offering personalized 1:1 dietetic advice.

Learn More About Joanna

More posts from Joanna Tsintaris | Registered Dietitian | MS Nutrition & Dietetics

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