How is creatine absorbed in the body?

Persky & Brazeau (2001) described that oral creatine monohydrate is absorbed primarily in the small intestine via a sodium-dependent transporter. Absorption is nearly complete, with bioavailability approaching 100% when taken in solution. Peak plasma creatine levels occur approximately 1-2 hours after ingestion.

How is creatine stored and distributed in the body?

Approximately 95% of the body's creatine is stored in skeletal muscle, with the remaining 5% distributed across the brain, heart, kidneys, liver, and testes. Within muscle, about two-thirds exists as phosphocreatine and one-third as free creatine. Total body creatine stores are approximately 120-140g in a 70 kg adult.

How is creatine eliminated from the body?

Creatine is non-enzymatically converted to creatinine at a rate of approximately 1.7% per day. Creatinine is then filtered by the kidneys and excreted in urine. This means approximately 2g of creatine is lost daily and must be replaced through diet and endogenous synthesis.

Persky & Brazeau 2001: Clinical Pharmacology of Creatine — Study Summary

Study Overview

Persky and Brazeau (2001) published a comprehensive pharmacological review of creatine monohydrate in Clinical Pharmacology and Therapeutics. This review treated creatine as a pharmaceutical agent, systematically examining its pharmacokinetics (absorption, distribution, metabolism, and excretion), pharmacodynamics (mechanism of action), drug interactions, and clinical applications. This approach provided a rigorous pharmacological framework for understanding creatine supplementation (RB et al., 2017) .

95%

of the body's total creatine is stored in skeletal muscle — the primary target tissue for supplementation

Persky & Brazeau, 2001

Key Findings

Near-complete oral bioavailability: Creatine monohydrate in solution is almost completely absorbed from the gastrointestinal tract, with peak plasma levels occurring 1-2 hours post-ingestion
Sodium-dependent transport: Creatine enters cells primarily through a specific sodium- and chloride-dependent creatine transporter (CrT/SLC6A8). This transporter is saturable, which explains why excessive single doses provide diminishing returns
Muscle is the primary storage site: Approximately 95% of body creatine resides in skeletal muscle, with total stores of 120-140g in a typical 70 kg adult
Constant turnover: Approximately 1.7% of the body’s creatine pool is converted to creatinine daily (about 2g/day), requiring constant replenishment through diet and endogenous synthesis
Saturation kinetics: Muscle creatine stores have an upper limit. Once saturated (typically 150-160 mmol/kg dry weight), additional creatine intake is excreted rather than stored
Co-ingestion with carbohydrates: The review noted that taking creatine with carbohydrates enhances insulin-mediated creatine uptake into muscle cells

Practical Implications

This pharmacological perspective provides important practical guidance for creatine users. Understanding that creatine transport is saturable explains why spreading doses throughout the day (or using smaller maintenance doses) is more efficient than taking large single doses.

The finding that carbohydrate co-ingestion improves creatine uptake supports the practical recommendation to take creatine with meals — Malaysian meals typically include rice or other carbohydrates, making meal-time dosing convenient and effective.

Understanding the daily turnover rate (~2g/day) also explains why 3-5g/day is the recommended maintenance dose — it replaces what is lost and gradually maximises muscle stores over 3-4 weeks without the need for a loading phase (RC et al., 1992) .

For Malaysian consumers, this pharmacological knowledge helps make informed decisions: choose creatine monohydrate (best studied form with near-complete bioavailability), take it with meals, use 3-5g/day consistently, and understand that individual response varies based on baseline stores and transporter expression.

Study Limitations

As a review article, it synthesised existing data rather than generating new experimental findings
Some pharmacokinetic parameters were derived from relatively small studies
The review focused primarily on creatine monohydrate — pharmacokinetics of alternative creatine forms were not extensively covered
Individual variation in creatine transporter expression was acknowledged but not fully characterised
Long-term pharmacokinetic adaptations (changes in transporter expression with chronic use) were not well understood at the time

Study Design and Methodology

Understanding how a study was designed helps assess the strength of its conclusions. Key methodological factors to evaluate include:

Sample size — larger studies (n=50+) provide more reliable results than small studies (n=10-15). Small sample sizes increase the risk of false positives and limit the ability to detect moderate effect sizes
Study duration — creatine research requires adequate duration for muscle saturation (minimum 4 weeks for maintenance dosing, 1 week for loading). Studies shorter than this may miss the full effect
Blinding — double-blind, placebo-controlled designs (where neither researchers nor participants know who receives creatine) are the gold standard for minimising bias
Population studied — results from trained athletes may not fully apply to untrained individuals, and vice versa. Age, sex, and dietary habits (particularly vegetarian status) also influence creatine response
Outcome measures — direct measures (muscle biopsy, MRS imaging) are more informative than indirect proxies (blood markers, performance tests) for assessing creatine uptake and metabolism

Clinical Implications and Practical Relevance

This research contributes to our understanding of creatine in several practical ways:

For athletes and fitness enthusiasts: The findings support the use of creatine monohydrate as a safe, effective ergogenic aid. The standard dosing protocol of 3-5g daily remains well-supported by the cumulative evidence base including this study.

For healthcare professionals: Understanding the specific mechanisms and safety data from studies like this helps clinicians provide evidence-based guidance to patients who ask about creatine supplementation. The research consistently shows a favourable safety profile at recommended doses.

For the Malaysian context: While most creatine research is conducted in Western populations, the fundamental biochemistry (ATP-phosphocreatine system) is universal. Malaysian consumers can apply these findings with confidence, adjusting for local factors like tropical climate (increased hydration needs) and halal dietary requirements (synthetic creatine monohydrate is permissible).

How This Fits Into the Broader Evidence

No single study should be used to make definitive claims about creatine supplementation. Instead, this research should be viewed as one piece of a much larger evidence base:

The ISSN Position Stand (2017) synthesises hundreds of studies into comprehensive recommendations
Multiple systematic reviews and meta-analyses confirm creatine’s effects on strength, power, and lean mass
Long-term safety data spanning up to 5 years shows no adverse effects at recommended doses

For a complete overview of the evidence, explore our Research Library which covers 60+ landmark creatine studies.

Sources & References

This page summarises Persky AM, Brazeau GA. Clinical pharmacology of the dietary supplement creatine monohydrate. Pharmacological Reviews. 2001;53(2):161-176.