Creatine With MK-677: The Lab Signal Is Not the Interaction

Start With the Marker, Not the Stack

Serum creatinine is used to estimate kidney filtration, but creatinine production also reflects creatine turnover, muscle mass, diet, and other non-kidney factors. A change in the marker is not automatically a change in filtration.

Elham Kabiri Naeini and colleagues summarized their 2025 systematic review and meta-analysis this way:

“Creatine supplementation is associated with a modest, transient increase in serum creatinine levels, likely due to metabolic turnover rather than renal impairment.”

The authors are kidney-disease and medical researchers at Isfahan University of Medical Sciences. Their review included 21 studies; 12 contributed to the creatinine meta-analysis and five to the GFR analysis. The excerpt concerns creatine, not ibutamoren, not their combination, and not every person with an elevated result (PMID 41199218; PMCID PMC12590749; DOI 10.1186/s12882-025-04558-6).

The same meta-analysis found no significant pooled difference in GFR, while noting that most included studies were short to moderate in duration and that longer-term evidence beyond one year was sparse. “Creatinine can move” and “kidney function is unaffected in every context” are not equivalent statements.

The Two-Column Evidence Problem

No direct coadministration PK, kidney-function, or performance trial was identified in FDA's ibutamoren review or the sources reviewed for this page. That absence rules out confident claims of “no interaction” just as much as it rules out confident claims of kidney damage.

What Ibutamoren Adds to the Decision

FDA's 2024 compounding review identified serious safety concerns in the available ibutamoren literature, including hyperglycemia, liver-enzyme elevations, edema, and fluid overload. It also found limitations in clinical evidence and gaps in bulk-substance characterization (FDA review, PDF pages 42–50).

In a randomized trial of healthy older adults, ibutamoren increased fat-free mass but also increased body weight and appetite, produced edema and muscle pain more often, increased fasting glucose, and reduced insulin sensitivity. Those results belong to that population and formulation; they do not establish a creatine interaction (PMID 18981485; PMCID PMC2757071).

Fluid retention can change body weight, and creatine can change creatinine interpretation. Neither observation proves that the two mechanisms add, cancel, or cause kidney injury when combined.

A Lab Interpretation Record

The useful original artifact here is not a self-directed testing schedule. It is the context a clinician needs if kidney results are being interpreted:

• the exact creatine product and amount actually used;
• when use began and whether a loading phase occurred;
• the exact ibutamoren product, source, and exposure history;
• prior kidney results, muscle mass, recent exercise, hydration, and diet context;
• other medicines or supplements that affect kidney function or creatinine; and
• symptoms or acute illness that change the urgency of evaluation.

Disclosing creatine use can prevent a marker from being interpreted without context. It should never be used to dismiss an abnormal result automatically. A clinician can decide whether repeat testing, a different filtration marker, urine testing, or urgent evaluation is appropriate for the actual situation.

Why the Legacy Protocol Was Not Supportable

The previous page prescribed an ibutamoren titration, a creatine amount, a staged start, hydration targets, laboratory thresholds, quarterly monitoring, and stop rules. It also declared the combination pharmacokinetically safe. No direct combination trial supplied those instructions.

The food and supplement audit explains the missing coadministration evidence. The exercise evidence map separates body composition from performance, and the young-adult safety page shows why cross-population findings cannot become an individualized monitoring schedule.

What Would Resolve the Question

A responsible combination study would use characterized products, report creatine intake before and during exposure, compare ibutamoren PK with and without creatine, measure directly or appropriately estimated GFR alongside creatinine, capture urine and adverse-event outcomes, and include enough follow-up to distinguish a transient marker change from harm.

Until such evidence exists, the defensible conclusion is: creatine has a known capacity to alter one common kidney marker; ibutamoren has separate unresolved safety and product-quality concerns; the combination itself has not been characterized.

Medical review of this revision is pending. FDA, investigators, institutions, journals, and study authors do not endorse creatine, ibutamoren, HealthRX.com, or this page.