Can I Take Creatine with Rezdiffra (Resmetirom)?

What Is Resmetirom (Rezdiffra) and Why Does It Matter for Supplement Choices?

Resmetirom is the first drug the FDA approved specifically for metabolic dysfunction-associated steatohepatitis (MASH), receiving accelerated approval in March 2024 under the brand name Rezdiffra. The drug selectively activates thyroid hormone receptor beta (THR-β) in the liver, reducing hepatic fat and fibrosis without the cardiac and bone effects of systemic thyroid hormone excess. Adults with MASH typically carry additional metabolic burdens: obesity, type 2 diabetes, dyslipidemia, and sarcopenia. That last point makes creatine supplementation particularly appealing to this population.

How Resmetirom Works in the Liver

By selectively binding THR-β, resmetirom increases mitochondrial fatty acid oxidation, lowers hepatic triglyceride synthesis, and reduces LDL cholesterol. In the key MAESTRO-NASH trial (N=966), resmetirom 100 mg daily produced MASH resolution without worsening fibrosis in 25.9% of patients versus 14.2% placebo at 52 weeks (P<0.001) [1]. Fibrosis improvement of at least one stage occurred in 26.0% versus 14.2% placebo (P<0.001) [1].

Why MASH Patients Reach for Creatine

Sarcopenia, defined as low skeletal muscle mass plus poor physical function, affects an estimated 20 to 35% of patients with advanced liver fibrosis [2]. Creatine monohydrate at 3 to 5 g/day raises phosphocreatine stores in muscle, increasing high-intensity exercise capacity and supporting lean mass preservation. These are legitimate therapeutic goals for people managing MASH, where physical activity is a cornerstone of care per the American Association for the Study of Liver Diseases (AASLD) 2023 practice guidance [3].

Does Creatine Interact Pharmacokinetically with Resmetirom?

The short answer is no. Resmetirom is metabolized primarily by CYP2C8 and, to a lesser extent, CYP3A4 [4]. Creatine is not a substrate, inducer, or inhibitor of either enzyme. Creatine is also not a significant transporter substrate for OATP1B1 or OATP1B3, the hepatic uptake transporters most relevant to resmetirom disposition. There is no documented competitive binding at plasma proteins between the two compounds.

What the Rezdiffra Prescribing Information Lists

The full Rezdiffra prescribing information (PI) approved by the FDA in March 2024 identifies strong CYP2C8 inhibitors (gemfibrozil), strong CYP3A4 inducers (rifampin), and OATP1B1/1B3 substrates as the drug classes warranting dose adjustment or avoidance [4]. Creatine monohydrate, creatine ethyl ester, and buffered creatine formulations appear on none of these interaction lists.

No dose-separation window is required. You do not need to take creatine at a different time of day from resmetirom on pharmacokinetic grounds.

The Real Issue: Creatine Elevates Serum Creatinine

This is where the clinical story gets meaningful. Creatine in muscle is non-enzymatically and irreversibly converted to creatinine, which is then excreted by the kidneys. When you load or maintain creatine supplementation, you produce more creatinine. This raises serum creatinine levels by roughly 10 to 20% and can lower calculated eGFR by a similar margin, without any actual kidney damage occurring [5].

Why That Matters on Rezdiffra

The Rezdiffra PI recommends baseline and periodic monitoring of renal function because THR-β activation affects metabolic pathways relevant to renal tubular handling of uric acid and organic anions [4]. If a patient starts creatine after their baseline creatinine was established, the prescriber may interpret a creatinine rise of 0.2 to 0.3 mg/dL as drug-induced nephrotoxicity when it is actually a benign supplement effect.

The inverse problem is equally concerning. A patient on creatine who develops early drug-related renal stress may have that signal masked if their creatinine appears stable relative to a creatine-supplemented baseline.

What the Research Shows on Creatine and Renal Markers

A 2003 randomized controlled trial by Poortmans and Francaux involving 100 subjects found no change in glomerular filtration rate, tubular reabsorption, or urinary protein excretion after creatine supplementation at doses up to 10 g/day for up to 5 years [5]. A 2021 systematic review in the Journal of Renal Nutrition (14 studies, N=470) confirmed that creatine does not cause renal structural damage in healthy adults with normal baseline kidney function, but explicitly noted that elevated serum creatinine can confound clinical interpretation [6].

The International Society of Sports Nutrition (ISSN) 2017 position stand states: "Creatine supplementation is not contraindicated in individuals with healthy kidney function, but laboratory values (serum creatinine, BUN) should be interpreted cautiously in supplementing individuals" [7].

Pharmacodynamic Interaction: Shared Metabolic Territory

Although there is no pharmacokinetic collision, resmetirom and creatine do share metabolic ground worth understanding.

Thyroid Hormone Receptor Beta and Creatine Kinase

THR-β regulates the expression of creatine kinase isoforms in skeletal and cardiac muscle [8]. Resmetirom's liver-selective activity means systemic CK levels are generally unaffected at therapeutic doses. In MAESTRO-NASH, mean serum CK did not rise to clinically concerning levels in the resmetirom arms [1]. Still, a patient adding high-dose creatine (20 g/day loading phase) while starting resmetirom could theoretically produce transient CK elevation that complicates interpretation of a muscle or cardiac enzyme panel. Using a maintenance dose of 3 to 5 g/day from the outset avoids the loading-phase spike.

Liver Safety Signal: Creatine Is Not Hepatotoxic at Standard Doses

Early case reports from the late 1990s raised concerns about creatine-related hepatotoxicity, but none were controlled for concurrent supplement use (particularly herbal thermogenics). A 2021 review in Nutrients found no credible hepatotoxicity signal from creatine monohydrate at 3 to 5 g/day in otherwise healthy individuals [9]. For MASH patients, this is reassuring. The liver is already under metabolic stress, and adding a genuinely hepatotoxic supplement would be a serious mistake. Creatine does not appear to be one.

Adulterated creatine products, particularly low-cost powders containing unlisted herbal extracts or stimulants, represent a real contamination risk. The FDA's Center for Food Safety and Applied Nutrition (CFSAN) has documented repeated cases of undisclosed drug and botanical ingredients in sports supplements [10]. Patients on Rezdiffra should select third-party certified products (NSF Certified for Sport or Informed Sport certification) to minimize contamination exposure.

Who Should Be Most Cautious?

Not every Rezdiffra patient faces the same risk profile from creatine.

Patients with Pre-existing CKD

MASH and chronic kidney disease (CKD) co-occur frequently. A 2022 analysis in the American Journal of Kidney Diseases found that MASH was present in 55% of biopsy-confirmed CKD cohorts, with metabolic syndrome as the shared driver [11]. In patients with eGFR <45 mL/min/1.73 m², the creatinine elevation from creatine supplementation may shift a patient from CKD stage 3a to 3b on paper, triggering unnecessary medication changes or referrals.

These patients should discuss creatine use specifically with their nephrologist before starting, and if they choose to supplement, should use cystatin C-based eGFR (which is not affected by dietary creatine intake) as the primary renal monitoring biomarker.

Patients Also Taking OATP-Sensitive Medications

Some MASH patients take statins that are OATP1B1 substrates (rosuvastatin, pravastatin). Resmetirom inhibits OATP1B1, which already raises statin exposure. Creatine does not add to this interaction, but it can independently raise CK in the presence of statin myopathy, complicating clinical attribution. If a patient reports muscle pain, the prescriber needs to disentangle statin-related myopathy, resmetirom-related CK changes, and exercise-induced CK from creatine supplementation.

Patients in the First 12 Weeks of Rezdiffra Treatment

The MAESTRO-NASH trial monitored LFTs at weeks 4, 12, 24, and 52 [1]. The Rezdiffra PI recommends discontinuation if ALT rises to more than 3 times the upper limit of normal during treatment [4]. This early monitoring window is when baseline laboratory values matter most. Starting creatine simultaneously with resmetirom introduces two new variables at once, making it harder to attribute any lab change to the correct cause. A reasonable clinical approach is to stabilize on resmetirom for at least 12 weeks and confirm stable liver and renal function before adding creatine.

Practical Guidance: What to Do If You Are Already Taking Both

Many patients arrive at a Rezdiffra prescription already using creatine. This is a common scenario given the fitness and metabolic health community's enthusiasm for creatine.

The HealthRX Creatine-on-Rezdiffra Decision Framework summarizes the four steps a clinician and patient should work through together:

1. Disclose immediately. Tell your prescriber the exact product, brand, dose (grams per day), and how long you have been taking it before your first Rezdiffra baseline labs are drawn.

2. Establish a creatine-supplemented baseline. If you have already been on creatine for at least 4 weeks at a stable dose, your baseline creatinine reflects that level. Document it clearly in the chart as "creatinine on X g/day creatine monohydrate."

3. Prefer cystatin C for renal monitoring. Ask your prescriber whether cystatin C-based eGFR can be used as a concurrent renal biomarker, particularly if your serum creatinine is already at the upper end of the reference range.

4. Avoid loading phases. Skip the 20 g/day, 5-to-7-day loading protocol. Go directly to 3 to 5 g/day maintenance dosing. This avoids the transient CK and creatinine spikes that loading produces and keeps laboratory trends interpretable.

If you were not taking creatine before starting Rezdiffra and want to add it, waiting 12 weeks lets your prescribing team confirm stable LFTs and eGFR before introducing a new confounding variable.

What Does the Evidence Say About Creatine and Liver Disease Specifically?

This is an area where direct trial data are thin. No published randomized controlled trial has evaluated creatine supplementation specifically in MASH or NAFLD patients taking resmetirom or any other liver-targeted drug. This absence of evidence is not the same as evidence of absence, but it does mean recommendations must be extrapolated from adjacent data.

Animal and Mechanistic Data

Several rodent studies have found that creatine supplementation reduces hepatic steatosis in choline-deficient diet models of NAFLD, possibly through preservation of S-adenosylmethionine (SAM) and reduction of hepatic lipid peroxidation [12]. These findings have not been replicated in human trials to a sufficient standard to make therapeutic claims. They do, however, suggest creatine is not prohepatotoxic in the context of fatty liver disease.

The AASLD Position on Dietary Supplements in MASH

The AASLD 2023 practice guidance on MASH states that "no dietary supplement has sufficient evidence to recommend for routine use in NAFLD/MASH" and advises clinicians to obtain a full supplement history given the potential for hepatotoxicity from unlisted botanical ingredients [3]. Creatine itself is not specifically flagged as harmful, but the guidance's emphasis on supplement disclosure underscores the monitoring approach described above.

Monitoring Schedule: A Concrete Plan

Given the considerations above, here is a practical lab monitoring schedule for patients on resmetirom who want to take creatine:

| Timepoint | Labs to Check | Notes | |---|---|---| | Before starting resmetirom | CMP (includes creatinine, eGFR), LFTs, lipid panel | If already on creatine, document dose in chart | | Week 4 on resmetirom | ALT, AST, creatinine | PI-recommended LFT check; compare to supplemented baseline | | Week 12 on resmetirom | Full CMP, LFTs, CK if muscle symptoms | Consider starting creatine after this visit if labs are stable | | Week 24 and 52 | Full CMP, LFTs, lipid panel | MAESTRO-NASH monitoring schedule [1] | | Any time symptoms arise | CK, creatinine, cystatin C, urinalysis | Muscle pain, dark urine, or edema requires prompt evaluation |

Key Drug Interactions Resmetirom Already Has (Context for Supplement Risk)

Understanding where resmetirom's known interactions lie helps calibrate how seriously to treat supplement additions.

The Rezdiffra PI lists gemfibrozil as contraindicated because it is a strong CYP2C8 inhibitor, raising resmetirom AUC approximately 2.3-fold [4]. Rifampin reduces resmetirom exposure by roughly 84% through CYP3A4 induction [4]. These are clinically significant pharmacokinetic interactions.

Creatine produces none of these enzyme-level effects. Its interaction concern is purely at the level of laboratory interpretation, a pharmacodynamic (specifically, a diagnostic confound) interaction rather than a change in drug exposure. This distinction matters: the risk is not that creatine makes resmetirom more toxic or less effective. The risk is that it makes lab results harder to read.

Summary of the Interaction Type

| Interaction Domain | Creatine + Resmetirom | |---|---| | CYP2C8 inhibition or induction | None | | CYP3A4 inhibition or induction | None | | OATP1B1/1B3 transporter effect | None | | Plasma protein binding competition | None | | Pharmacodynamic toxicity overlap | Low; no shared organ toxicity | | Laboratory confound | Yes: creatinine elevation 10 to 20%, CK elevation with loading phase | | Hepatotoxicity risk from creatine | Not established at 3 to 5 g/day monohydrate |