Mounjaro® and kidney stones

What each document says

We searched the US prescribing information, the European product information and the Canadian monograph for kidney stones, nephrolithiasis and urolithiasis and found no entry ^[1][3][4]. What all three do contain is a kidney warning about fluid loss.

What tirzepatide trials and studies show

Two meta-analyses pooled randomised tirzepatide trials. The first, 15 trials with 14,471 people with or without diabetes, found that tirzepatide did not raise the risk of nephrolithiasis, urinary infections, acute kidney injury or kidney adverse events compared with placebo, insulin or GLP-1 medicines ^[5]. The second, 20 trials with 15,905 people, found no significant difference in a combined kidney outcome that included kidney stones (risk ratio 1.22, not statistically significant), with similar results by dose and indication ^[6]. Trials last one to two years and stones are uncommon, so small differences could still be missed; the second team said longer-term safety cannot yet be settled ^[6].

A study of 44 people with a history of stones who lost weight on GLP-1-based medicines, including dual GIP/GLP-1 agonists, compared 24-hour urine before and during treatment. Urine oxalate fell, and stone-forming saturation did not rise; the authors described these medicines as a safe weight-loss option for stone formers on that basis ^[7]. It was small and retrospective.

In the other direction, a study of US Department of Veterans Affairs records compared people with diabetes starting GLP-1 receptor agonists with usual care and found more nephrolithiasis among GLP-1 users ^[8]. The summary does not report tirzepatide separately, and an observational study cannot rule out that the groups differed in other ways.

How stones and treatment could connect

• Supported by the label: nausea, vomiting and diarrhea are common, most often while the dose is being raised, and can lead to dehydration ^[1]. MedlinePlus calls not drinking enough the biggest risk factor for stones ^[10].
• Proposed: eating and drinking less, a common effect of reduced appetite, could lower urine volume. This has not been measured for stones on tirzepatide.
• Diet shifts: people on weight treatment are often encouraged to eat more protein. The NIH notes that animal protein and sodium can raise stone risk for some stone types, while being overweight raises it too ^[12].
• Background risk: a 2026 review describes obesity, type 2 diabetes and metabolic syndrome as linked to stones through insulin resistance, more acidic urine and higher urinary oxalate, calcium and uric acid ^[9]. Many Mounjaro® users start with this risk.

Other reasons stones form

Stones form when urine carries too much of substances such as calcium, oxalate and phosphorus ^[11]. Calcium stones are the most common type. Others include uric acid stones, linked to gout; struvite stones after repeated urinary infections; and cystine stones in an inherited condition ^[10]. Some stone types run in families, and diseases of the small intestine raise the risk of calcium oxalate stones ^[10].

Oxalate is found in foods such as spinach, rhubarb, nuts and wheat bran, and in vitamin C supplements ^[10][12]. If you have had a stone before, ask which type it was, because diet advice differs by type ^[12].

Recognising a stone

A stone often causes no symptoms until it moves into the tube that drains the kidney. Then the typical sign is severe pain that starts and stops suddenly, in the side or back, sometimes moving to the lower abdomen or groin ^[10]. Other signs include blood in the urine, which may look pink, red or brown, a constant urge to urinate, pain when passing urine, cloudy or bad-smelling urine, nausea, vomiting, fever and chills ^[10][11].

Severe stomach pain on Mounjaro® has other possible causes that the label covers, including pancreatitis, with pain that may spread to the back, and gallbladder problems ^[1][2]. Pain that comes in waves and travels towards the groin points more towards a stone, but only an examination can tell.

Lowering the chance of a stone

The Mounjaro® documents do not give stone-prevention advice. The NIH and MedlinePlus say the following; check any change with your clinician, particularly if you have kidney disease or a fluid limit.

• Drinking enough liquid, mainly water, is the most important step; how much is right for you is a question for your clinician ^[12].
• Be extra careful about fluids on days with vomiting or diarrhea, and tell your provider if they do not stop ^[1][2].
• Limit high-sodium canned, packaged and fast foods ^[12].
• If you have had a stone, ask which type, and talk with a clinician or dietitian about protein, calcium and oxalate before changing your diet ^[12].
• Ask before taking high-dose vitamin C supplements, a source of oxalate ^[10].

Mounjaro® is a registered trademark of Eli Lilly and Company. PepLabo is not affiliated with or endorsed by Eli Lilly and Company.