How does obesity cause kidney stones?

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Learn about the link between obesity and kidney stones, and whether weight loss medication can help to reduce risk.

Kidney stones are common. They are also painful.

Research shows that people living with obesity are more likely to develop kidney stones than those of a lower body weight.¹ But why?

The answer lies in how excess body fat affects metabolism, urine chemistry and overall health.

In this guide, we explain:

What kidney stones are
Their symptoms and complications
How obesity increases risk
Whether weight loss medications like Mounjaro and Wegovy can help

What are kidney stones?

Kidney stones are hard, crystal-like deposits that form inside the kidneys.

They develop when certain minerals and salts in urine become highly concentrated and stick together. Over time, these crystals can harden into stones.

There are a few different kinds. The most common are calcium oxalate stones, but there are also uric acid stones, struvite stones and the rarer cystine stones.

Stones can stay in the kidney or travel into the ureter (the tube connecting the kidney to the bladder). When they move, they can cause considerable pain.

Symptoms of kidney stones

Small stones may cause no symptoms at all. However, larger stones can lead to:

Severe pain in the lower back or side
Pain that radiates to the groin
Nausea and vomiting
Blood in urine
Frequent or painful urination
Fever, if an infection develops

The pain, often called renal colic, can come in waves and may be intense. And if an infection occurs alongside a blockage, it becomes a medical emergency.

How common are kidney stones?

Very common. Kidney stones affect around one in 10 people at some point in their lives.²

The risk is higher in men, those with a family history of kidney stones, people living with diabetes and people living with obesity.

In the last few decades, rates of kidney stones have increased.³ Rising obesity levels are believed to be part of the reason.

How does obesity increase the risk of kidney stones?

Obesity's link to kidney stones is down to the metabolic changes that occur alongside excess body fat. For example:

1. Changes in urine composition

People living with obesity are more likely to have:

Higher levels of calcium in their urine
Higher levels of oxalate
Higher levels of uric acid
Lower urine pH, meaning their urine is more acidic

These changes increase the likelihood that crystals will form.

Uric acid stones, in particular, are more common in people with obesity and insulin resistance.

2. Insulin resistance and acid levels

Obesity is strongly linked to insulin resistance.

Insulin resistance affects how the kidneys handle acid. It can lower urine pH, promoting uric acid stone formation.

This metabolic pathway helps explain why kidney stones are more common in people with type 2 diabetes and metabolic syndrome.

3. Chronic low-grade inflammation

Excess body fat is metabolically active. That means it produces inflammatory chemicals that affect the whole body.

Chronic inflammation can influence kidney function and mineral balance, contributing to stone formation.

4. Dietary habits

Obesity doesn't cause kidney stones on its own. Some nutritional patterns associated with weight gain can be a factor.

Diets high in salt, processed foods, sugary drinks and animal protein can increase kidney stone risk.

Low fluid intake is another major factor. Dehydration concentrates the urine, making stone formation more likely.

Complications of kidney stones

Most small stones pass on their own.

However, complications can include recurrent stones, urinary tract infections and even long-term kidney damage from repeated blockages.

You should seek urgent medical care if you experience:

Severe, persistent pain
Fever alongside urinary symptoms
Inability to pass urine
Blood in the urine

If you have had kidney stones before, discussing prevention with a GP or specialist is advisable.

People who develop one kidney stone are at increased risk of developing another. This makes prevention important.

Can weight loss reduce the risk?

In many cases, yes.

Losing excess weight can improve:

Insulin sensitivity
Urine pH balance
Inflammation
Blood sugar control

These improvements may reduce the metabolic drivers of stone formation.

Crash dieting is not recommended. Very rapid weight loss or high-protein/low-carb crash diets may actually temporarily increase the risk of kidney stones in some people.

Gradual, medically supervised weight loss is much safer.

Can Mounjaro or Wegovy help?

Mounjaro (tirzepatide) and Wegovy (semaglutide) are medications designed to support weight loss by reducing appetite and improving blood sugar regulation.

In clinical trials:

Tirzepatide users lost an average of 21% of their starting body weight over 72 weeks⁴
Semaglutide users lost an average of 15% of their starting body weight over 68 weeks⁵

Significant weight reduction can improve metabolic health markers linked to kidney stone formation, including insulin resistance and inflammation.

However, it's important to note that these medications are not preventative or direct treatments for kidney stones. Through sustained weight loss and improved metabolic function, they may have indirect benefits.

If you have a history of kidney stones, it is important to discuss this with a prescribing medical professional before starting any medication.

Practical steps anyone can take to reduce kidney stone risk

While the risk may be higher for people living with obesity, kidney stones can affect anyone. Here are some prevention strategies everyone can take:

Stay well hydrated: aim for clear or pale yellow urine. Diluted urine reduces crystal formation.
Reduce excess salt: high sodium increases calcium in urine.
Eat balanced protein: extremely high animal protein intake may increase stone risk in some individuals.
Maintain a healthy weight: gradual, sustainable weight loss can reduce metabolic risk factors.
Go easy on the sugar: improving insulin sensitivity supports healthier urine chemistry.

The bigger picture

Kidney stones are unpleasant, but they are also a signal from your body – they often reflect underlying metabolic stress.

For people living with obesity, the increased risk of kidney stones is one of several health complications linked to insulin resistance and chronic inflammation.

Sustainable weight loss, whether achieved through lifestyle changes alone or with medications like Mounjaro or Wegovy, may help to reduce this risk over time.

Semapen's weight loss programmes are designed and led by UK obesity experts, including Professor David Kerrigan, former president of the British Obesity & Metabolic Specialist Society. Do you want to lose weight with structured clinical support? It's quick and easy to get started in the SemaPen app.

Sources

1. Taylor, E.N. et al. (2005) "Obesity, weight gain, and the risk of kidney stones" JAMA, 293(4) https://doi.org/10.1001/jama.293.4.455

2. National Kidney Foundation (2025) Kidney Stones. Retrieved from https://www.kidney.org/kidney-topics/kidney-stones

3. Romero, V. et al. (2010) "Kidney Stones: A Global Picture of Prevalence, Incidence, and Associated Risk Factors" Reviews in Urology, 12(2–3) https://pubmed.ncbi.nlm.nih.gov/20811557/

4. Jastreboff, A.M. et al. (2022) "Tirzepatide Once Weekly for the Treatment of Obesity" The New England Journal of Medicine, 387(3) https://doi.org/10.1056/NEJMoa2206038

5. Wilding, J.P.H. et al. (2021) "Once-Weekly Semaglutide in Adults with Overweight or Obesity" The New England Journal of Medicine, 384(11) https://doi.org/10.1056/NEJMoa2032183

This article was reviewed and approved by Lujain Alhassan, Bariatric Nutritionist, on 28 February 2026.

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