Tirzepatide: Effect on the Liver and Kidneys

Tirzepatide is usually discussed in the context of weight and glucose, but the liver and kidneys are organs it affects no less significantly. For the liver the data are mostly reassuring; for the kidneys the picture is twofold: long-term markers improve, while short-term risks are related to dehydration. The editorial team has gathered what is known from clinical studies.

Why the liver and kidneys matter for assessing tirzepatide

Most tablet medications pass through the liver, where they are metabolized by enzymes, and are excreted by the kidneys. Tirzepatide is arranged differently: it is a peptide that is broken down by proteolysis throughout the body, and the breakdown products are excreted in urine and feces. So it does not require dose adjustment in impaired liver or kidney function — this is stated in the prescribing information.

However, the absence of a need to adjust the dose does not mean the absence of an effect. People with obesity and type 2 diabetes — exactly those who are prescribed tirzepatide — have a high frequency of metabolic-associated fatty liver disease and diabetic kidney disease. So any drug for this group is assessed through the prism of these organs as well.

The effect of tirzepatide on the liver and kidneys is mostly indirect. Weight loss, improved insulin sensitivity, reduced glucose and pressure unload both organs. At the same time, digestive side effects can temporarily create risks for the kidneys that are absent in the «calm» phase of treatment.

It is worth distinguishing separately between supervised medical use and self-directed use for weight loss against a background of a strict diet, stimulants and diuretics. In the latter case, the favorable effects may be outweighed by risks that studies simply did not investigate.

Fatty liver disease: what the studies showed

Metabolic-associated fatty liver disease (MASLD, formerly NAFLD) is the accumulation of fat in hepatocytes, which in some people progresses to inflammation (steatohepatitis, MASH) and fibrosis. The basis of treatment remains weight loss, and it is precisely here that tirzepatide demonstrates a powerful effect.

In the SURPASS-3 MRI substudy in patients with type 2 diabetes, liver fat content was measured using magnetic resonance imaging. On tirzepatide it decreased much more strongly than in the insulin degludec group, and the decrease correlated with the loss of weight and visceral fat.

Even more important data were obtained in the phase 2 randomized trial SYNERGY-NASH, published in the New England Journal of Medicine in 2024. In patients with biopsy-confirmed steatohepatitis and fibrosis, tirzepatide over 52 weeks led more often than placebo to the resolution of steatohepatitis without worsening of fibrosis. These are still interim data, and phase 3 studies are needed for final conclusions.

In clinical studies a decrease in the liver enzymes ALT and AST was also recorded, which usually reflects a reduction in inflammation. No cases of drug-induced hepatitis clearly associated with tirzepatide were described in the registration studies.

Kidneys: albuminuria and filtration rate

To assess the state of the kidneys, two main parameters are used: the estimated glomerular filtration rate (eGFR), which reflects the kidneys' «throughput», and the albumin/creatinine ratio in the urine, which indicates damage to the filtration barrier. Both markers are prognostically important in diabetes.

A post-hoc analysis of the SURPASS-4 trial, in which tirzepatide was compared with insulin glargine in patients with type 2 diabetes and high cardiovascular risk, showed a slower decline in eGFR and a reduction in albuminuria on tirzepatide. A composite renal outcome that included the appearance of macroalbuminuria also occurred less often.

These data are consistent with the results for other GLP-1 agonists. In particular, for semaglutide a dedicated study of renal outcomes, FLOW, has already been completed. For tirzepatide, analogous dedicated studies are ongoing, so the conclusions so far are based on secondary analyses.

The mechanisms of nephroprotection are explained by the reduction of glucose, arterial pressure and body weight, as well as possible direct anti-inflammatory effects. At the start of therapy a slight hemodynamic fluctuation of eGFR is sometimes observed, which does not in itself indicate damage.

Acute kidney injury and the gallbladder

The prescribing information for tirzepatide contains a warning about acute kidney injury. The mechanism is not toxic but prerenal: with pronounced nausea, vomiting or diarrhea, the body loses fluid, the volume of circulating blood decreases, and the kidneys receive less blood. In people with chronic kidney disease such an episode can cause a sharp deterioration in function.

The risk is highest in the first weeks of treatment and after a dose increase, when gastrointestinal symptoms are strongest. It increases against the background of drugs that affect renal hemodynamics: diuretics, ACE inhibitors, angiotensin receptor blockers and non-steroidal anti-inflammatory agents.

The second problem, related to the hepatobiliary system, is gallstone disease and cholecystitis. Rapid weight loss itself increases the risk of stone formation, and GLP-1 agonists can affect gallbladder motility. In the SURMOUNT studies such events occurred more often than in the placebo groups, although overall they remained uncommon.

Symptoms that require seeing a doctor: severe pain in the right hypochondrium or upper abdomen, pain radiating to the back, jaundice, a sharp decrease in the amount of urine, pronounced weakness and thirst against a background of vomiting.

• Drink enough fluid, especially on days with nausea or diarrhea.
• Do not take NSAIDs «just in case» without need.
• With prolonged vomiting, consult a doctor rather than waiting for it to pass.
• Inform the doctor about a history of gallstone disease or pancreatitis.

Who needs particular caution

Patients with chronic kidney disease can receive tirzepatide without dose adjustment, but require more frequent monitoring of creatinine and electrolytes during periods of titration. Experience of use in end-stage renal failure is limited.

For people with liver cirrhosis the drug is prescribed with caution: there is little data on decompensated cirrhosis, and the risks associated with dehydration and inadequate nutrition are higher in them. The SYNERGY-NASH study included patients with fibrosis, but not with decompensated cirrhosis.

A separate risk group is people who use tirzepatide outside medical supervision together with aggressive calorie restriction, diuretics, stimulants or anabolic steroids. The latter in themselves can damage the liver and increase pressure, and the combination with dehydration creates a scenario for the kidneys that was not studied in any trial.

Finally, people with alcoholic liver disease or alcohol abuse should remember the risk of pancreatitis: alcohol and GLP-1 agonists are among the factors that should not be combined without discussion with a doctor.

Editorial conclusions

For the liver, tirzepatide looks rather like an ally: studies show a reduction in liver fat and signs of regression of steatohepatitis, although phase 3 data are still awaited.

For the kidneys, long-term markers — albuminuria and the rate of decline in filtration — improve, but in the short term dehydration due to side effects can cause acute kidney injury.

A sensible approach is baseline tests of liver and kidney function, hydration control during periods of titration and attention to symptoms from the gallbladder and pancreas.

We also recommend reading our materials on tests during the medical use of tirzepatide, on its interactions with other drugs and on the specifics of therapy in women.

References

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2. Gastaldelli A, Cusi K, Fernández Landó L, et al. Effect of tirzepatide versus insulin degludec on liver fat content and abdominal adipose tissue in people with type 2 diabetes (SURPASS-3 MRI). Lancet Diabetes Endocrinol. 2022;10(6):393–406.
3. Heerspink HJL, Sattar N, Pavo I, et al. Effects of tirzepatide versus insulin glargine on kidney outcomes in type 2 diabetes in the SURPASS-4 trial: post-hoc analysis of an open-label, randomised, phase 3 trial. Lancet Diabetes Endocrinol. 2022;10(11):774–785.
4. Del Prato S, Kahn SE, Pavo I, et al. Tirzepatide versus insulin glargine in type 2 diabetes and increased cardiovascular risk (SURPASS-4). Lancet. 2021;398(10313):1811–1824.
5. Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide once weekly for the treatment of obesity. N Engl J Med. 2022;387(3):205–216.
6. Mounjaro (tirzepatide) injection. Prescribing information. Eli Lilly and Company; U.S. Food and Drug Administration.