Does Ozempic cause kidney stones? What the urine data shows

The short answer

There is no solid evidence that GLP-1 medications cause kidney stones. In the one study that measured it directly, weight loss on semaglutide and tirzepatide lowered urine oxalate, a main driver of the most common stones, and did not worsen the urine chemistry behind stone formation. That is the opposite of what weight-loss surgery tends to do.

Kidney stones are one of those problems that rewrite your habits. Once you have had one, you drink more water, you read ingredient labels, and you brace yourself against anything that might bring on another. So if you are starting Ozempic, Wegovy, or Mounjaro, it is fair to ask whether rapid weight loss puts your kidneys back in the firing line. Here is what the data actually says.

Why people worry about kidney stones on a GLP-1

Carrying extra weight is itself a risk factor for kidney stones. Obesity shifts urine chemistry in ways that make stones more likely, which is part of why stone formers are often told to lose weight in the first place.

The catch is how you lose it. Weight-loss surgery, especially gastric bypass, is well known to raise urinary oxalate and increase kidney stone risk, a problem doctors call enteric hyperoxaluria. That track record is why many people assume any fast weight loss, including the kind GLP-1 medications produce, carries the same danger. The real question is whether the drugs behave like surgery or not.

What the 2024 urine study found

Researchers at UT Southwestern Medical Center set out to answer exactly that. In a study published in Kidney360 in 2024, Feghali and colleagues reviewed 44 obese adults who already formed kidney stones and who then lost weight on GLP-1-based therapy, meaning semaglutide or the dual GLP-1/GIP drug tirzepatide.

Each person had at least two 24-hour urine collections, one before and one during weight loss, so their own urine chemistry could be compared over time. Over a median of 1.1 years, they lost an average of 6.6 kg (about 14.6 lb). Here is what happened to the markers that drive stones:

• Urine oxalate fell from 40 to 32 mg per day (P = 0.002), a meaningful drop in one of the main building blocks of the most common stones.
• Urine sulfate and ammonium also fell, both signs of a lower acid load on the kidneys.
• Urine calcium, citrate, uric acid, pH, and total volume did not change significantly.
• The supersaturation indices for calcium oxalate, calcium phosphate, and uric acid, which estimate how primed the urine is to crystallise, showed no significant change.

The authors concluded that weight loss through GLP-1-based therapy was not associated with prolithogenic changes, meaning changes that promote stones, unlike other weight-loss methods. In plain terms, the urine did not become more stone-prone, and on at least one measure it improved.

Why a drop in urine oxalate matters

Most kidney stones are made of calcium oxalate. Oxalate binds with calcium in the urine, and when there is enough of it, it forms the crystals that grow into stones. Less oxalate in the urine generally means fewer raw materials for that process.

This is the exact point where GLP-1 medications and weight-loss surgery appear to part ways. Gastric bypass can push oxalate up because of how it changes fat absorption in the gut. In the UT Southwestern data, GLP-1 weight loss did the reverse and nudged oxalate down. Early findings like these suggest the route to weight loss matters as much as the weight loss itself, at least for stone risk.

What this study does not prove

This is reassuring, but it is one small study, and it is worth being honest about the limits before you file the worry away for good.

• It was retrospective and from a single clinic, so it shows an association over time, not cause and effect.
• It included only 44 people, all of them obese and all already stone formers, so it may not reflect everyone on these drugs.
• It measured urine chemistry, which predicts stone risk, not actual stones. No one counted how many stones formed.
• The median follow-up was about one year, which is short for a condition that can take years to come back.
• It grouped semaglutide and tirzepatide together, so it cannot say whether one is better than the other for your kidneys.

So the fair summary is this. The best evidence available points away from GLP-1 medications raising stone risk, and researchers are still filling in the picture. That is a long way from a reason to worry, but it is not a cast-iron guarantee either.

Signs of a kidney stone to watch for

Most small stones pass on their own, but knowing the warning signs means you can act early instead of guessing. A stone tends to announce itself the moment it starts to move through the urinary tract.

• Sharp pain in your side or back, below the ribs, that can spread to your lower belly and groin.
• Pain that comes in waves and shifts in intensity as the stone moves.
• Pain or burning when you urinate, or a sudden, frequent urge to go.
• Urine that looks pink, red, or brown, or that turns cloudy or smells strong.
• Nausea and vomiting that arrive alongside the pain rather than on their own.

Call your doctor if the pain is severe or will not settle. Pain with a fever and chills can signal an infection sitting behind a blocked stone, and that needs urgent care rather than a wait-and-see approach. Keep in mind that nausea is also a common GLP-1 side effect on its own, so pain is the signal that sets a stone apart.

How to lower your kidney stone risk on a GLP-1

Whatever the drug does, the basics of stone prevention still carry most of the weight. One detail from the study matters here: urine volume did not rise during weight loss, which means the medication will not hydrate you for you. That part is still your job.

1. Drink enough to stay ahead of thirst. Most stone formers are told to aim for pale urine, which often means roughly 2.5 litres of fluid a day. GLP-1 medications can blunt thirst along with appetite, so build water into your routine instead of waiting to feel it.
2. Do not crash-diet on top of the drug. The medication already lowers how much you eat. Stacking an extreme diet on top can push weight loss faster than your body handles well and strip away more lean mass than fat.
3. Keep protein adequate, not extreme. Protein protects muscle during weight loss, but very high animal-protein intakes can raise stone risk in some people. Steady, moderate protein spread across the day is the safer target.
4. Mind your nutrient gaps. Rapid weight loss on any GLP-1 medication can leave you short on vitamin B12, vitamin D, and iron, which is one of the GLP-1 side effects people most often overlook. A simple monitoring plan catches these before they turn into symptoms.
5. Tell your doctor if you have had a stone. If you are a known stone former, a 24-hour urine test before and during treatment, exactly what this study used, can track your own risk rather than leaning on averages.

Closing nutrient gaps during fast weight loss is the whole reason GLP-1 Shield exists. No supplement treats or prevents kidney stones, and nothing here replaces your doctor's advice, but keeping your nutrition steady is one of the few things fully in your control while the medication does its work. For the wider picture, see our look at what GLP-1 drugs do for your kidneys and our vitamin monitoring guide for GLP-1 users.

Frequently asked questions

Does Ozempic cause kidney stones?

No current evidence shows Ozempic causes kidney stones. In a 2024 Kidney360 study of 44 obese stone formers, weight loss on semaglutide or tirzepatide lowered urine oxalate (40 to 32 mg/day) and did not worsen stone-forming urine chemistry. The study was small and retrospective, so researchers are still confirming the picture.

Is GLP-1 weight loss safer for kidney stones than weight-loss surgery?

Early evidence suggests it may be. Gastric bypass is known to raise urinary oxalate and stone risk, while the 2024 UT Southwestern study found GLP-1 weight loss lowered oxalate instead. The two routes to weight loss appear to affect stone chemistry differently, though no trial has compared them head to head.

Should I drink more water on Ozempic?

Yes. In the 2024 study, urine volume did not rise during GLP-1 weight loss, so the drug does not hydrate you on its own. Because GLP-1 medications can blunt thirst, most stone formers are advised to drink enough for pale urine, often around 2.5 litres a day.

Can I take a GLP-1 if I have had kidney stones?

That is a decision for your doctor, but a history of stones is not a known reason to avoid GLP-1 medications. The current data on stone-forming urine chemistry is reassuring. If you are a known stone former, ask about a 24-hour urine test before and during treatment to track your own risk.