Why Cats Are at Higher Risk for Urinary Stones and How Pet Parents Can Prevent Them

Urinary stones are more common in cats than many pet parents realize, and they can quickly turn into a life‑threatening emergency. Learn what really causes feline urinary stones, the subtle signs you should never ignore, and the daily habits that can help keep your cat’s bladder healthy.

Urinary stones are a painful condition in which certain substances in the urine crystallize and form “stones” inside the kidneys, bladder, ureters, or urethra. These stones can range from a few millimeters to several centimeters in size. In cats, urinary stones are a major part of what veterinarians call feline lower urinary tract disease (FLUTD), a group of conditions that affect the bladder and urethra.

When stones rub against or block the urinary tract, they can cause inflammation, bleeding, and intense pain. In severe cases, especially in male cats, stones can completely block the urethra and prevent urine from passing. This is a true emergency that can become life‑threatening within a couple of days.

Among the different types of urinary stones, two are especially common in cats. Struvite stones (magnesium ammonium phosphate) tend to form when urine becomes more alkaline, while calcium oxalate stones are more likely to form in more acidic urine. Together, these two types account for well over 80 percent of urinary stones seen in cats.

Understanding what drives these stones to form is the first step toward protecting your cat.

What Really Causes Urinary Stones in Cats

Veterinary experts generally group the causes of urinary stones into two broad categories. The first is shifts in urine pH, meaning the urine becomes too acidic or too alkaline. The second is an excess of stone‑forming minerals in the body, such as magnesium and calcium.

Both factors tend to be influenced by diet, hydration, and overall health. When urine pH drifts out of its ideal range and stone‑forming minerals are present in high enough concentrations, crystals can start to form and gradually grow into stones.

How Diet Affects Your Cat’s Urine pH

In both humans and animals, everyday eating habits have a major impact on the body’s acid–base balance and, in turn, on urine pH. While there are individual differences, nutrition research offers some general patterns:

• Diets higher in vegetable ingredients tend to push urine pH upward, making it more alkaline.
• Diets richer in meat and fish tend to lower urine pH, making it more acidic.

Cats are natural carnivores, and high‑quality complete and balanced commercial cat foods are formulated with this in mind. When a cat eats only an appropriate complete diet designed for cats, urine pH usually stays within a healthy range.

However, problems can arise when pet parents frequently offer homemade meals, table scraps, or large amounts of treats that are not nutritionally balanced. These extras can shift urine pH in an unhealthy direction and increase the risk of stone formation over time.

Why Urine pH Shifts Throughout the Day

Even with a good diet, urine pH is not fixed. It naturally fluctuates in response to meals and other factors. For example, when a cat eats, the stomach produces acid to help digest food. To supply this stomach acid, the body temporarily shifts acid from other areas, which can make the urine more alkaline for a period after eating.

If a cat eats a large amount of food in one sitting, this post‑meal alkalinization can be more pronounced. More alkaline urine can create a favorable environment for struvite crystals to form, especially if magnesium levels are also high.

Many veterinarians therefore recommend feeding measured portions in smaller, divided meals rather than offering one large meal per day. For many households, splitting the daily ration into two meals, morning and evening, works well and may help reduce extreme swings in urine pH.

The Hidden Role of Minerals in Urinary Stones

Urinary stones cannot form without their building blocks. In cats, two key mineral players are:

• Magnesium, which is a major component of struvite stones
• Calcium, which is a major component of calcium oxalate stones

Minerals are essential nutrients and part of the five major nutrient groups, so they are not inherently harmful. The problem arises when a cat consumes too much of certain minerals or when the balance of minerals in the body is disrupted. Under these conditions, excess minerals can combine with other substances in the urine and form crystals.

This is why feeding a complete and balanced cat food formulated for urinary health can be so important, especially for cats that have had stones before. These diets are designed to carefully control mineral levels and support a more favorable urine environment.

Concentrated Urine Makes Stones More Likely

Even if urine pH and mineral intake are reasonably well controlled, stones are more likely to form when urine becomes very concentrated. When a cat does not drink enough water, they urinate less often, and the urine that does collect in the bladder becomes more concentrated with minerals and waste products.

Over time, this concentrated urine greatly increases the chances that crystals will form and grow into stones. Encouraging your cat to drink more and urinate regularly is therefore one of the most powerful preventive steps you can take.

Cats are naturally prone to low water intake. Their wild ancestors, such as the African wildcat from arid North African regions, evolved to survive on relatively little free water, obtaining much of their moisture from prey. As a result, many modern housecats do not instinctively drink large amounts of water, especially if they eat mostly dry food.

This evolutionary background helps explain why cats develop urinary stones more often than dogs. The risk can be even higher in winter, when many cats drink less because the weather is cooler. During colder months, pet parents may want to offer more wet food, add water to meals, or use water fountains to help maintain good hydration.

Digestive upsets can also play a role. Diarrhea can lead to extra fluid loss, which may further concentrate the urine. Avoiding foods that commonly upset your cat’s stomach and seeking veterinary advice for ongoing digestive issues can indirectly support urinary health.

Other Risk Factors You Should Know

Several additional factors can increase a cat’s risk of urinary stones.

Excess weight and low activity levels are important contributors. Overweight cats often move less, which can mean they drink less and urinate less frequently. In some cases, excess body fat around the pelvis may also narrow the urethral passage, making it easier for stones or plugs to cause an obstruction.

Bladder infections and inflammation can also change the urine environment. Certain bacteria can make urine more alkaline, which favors the formation of struvite crystals. Even when bacteria are not present, inflammation of the bladder lining can contribute to discomfort and urinary problems that may accompany stones.

Sex also matters. Male cats are at higher risk of dangerous blockages than females. While both males and females can develop stones, the male urethra is longer, narrower, and has more curves. The tip is especially narrow, which makes it easier for stones or plugs to become lodged and block urine flow. When this happens, the condition can worsen rapidly and requires immediate veterinary care.

Mineral Water and Cats What Pet Parents Need to Know

Many people associate the word “minerals” with bottled mineral water and may have heard that mineral water can be dangerous for cats and dogs. The reality is more nuanced.

Water is often classified by hardness, which reflects its mineral content, especially calcium and magnesium. Water with higher mineral content is called hard water, while water with lower mineral content is called soft water.

For pets prone to urinary stones, very hard water is generally not recommended, because it can contribute additional minerals that may end up in the urine. However, in many countries, including Japan, most commercially sold bottled waters are actually soft waters, chosen to match local taste preferences.

In fact, in some regions, tap water can contain more minerals than many bottled soft waters. This means that, depending on where you live, bottled soft water may not be any more risky than tap water and may even contain fewer minerals.

For cats with a history of urinary stones, veterinarians often suggest choosing water with a lower hardness level whenever possible. If you use bottled water, check the label for mineral content and hardness. If you rely on tap water, your local water authority may provide hardness information.

The key is not to fear all mineral water, but to avoid high‑hardness water for cats that are already vulnerable to urinary issues.

Common Signs of Urinary Stones in Cats

Urinary stones can cause a range of symptoms, some subtle and some very obvious. Pet parents should watch for:

• Frequent urination
• Straining to urinate or passing only small amounts of urine at a time
• Spending a long time in the litter box, often in a crouched position
• Blood in the urine (pink, red, or brown discoloration)
• Urinating outside the litter box, such as on beds, rugs, or near the box
• Restlessness, agitation, or signs of discomfort

Certain signs indicate a true emergency and require immediate veterinary attention:

• Crying out or vocalizing in pain while trying to urinate
• Producing no urine at all, despite repeated attempts
• A firm, swollen lower abdomen that feels tight or distended

When a stone or plug completely blocks the urethra, the cat enters a state called urethral obstruction. If this continues for more than about 24–48 hours, toxins that are normally removed in the urine build up in the bloodstream, leading to uremia (uremic poisoning). Without rapid treatment, this condition can be fatal.

If you ever suspect your cat may be blocked, do not wait and see. Seek emergency veterinary care immediately.

How Veterinarians Treat Urinary Stones

Treatment depends on the type, size, and location of the stones, as well as the cat’s overall condition. For smaller struvite stones, veterinarians often recommend a combination of prescription urinary diets and medications designed to help dissolve the stones over time and reduce inflammation.

When larger stones form in the bladder or kidneys, or when stones do not respond to medical dissolution, surgical removal may be necessary. This allows the veterinarian to physically remove the stones and relieve discomfort or obstruction.

If a stone or plug becomes lodged in the urethra and blocks urine flow, the immediate priority is to relieve the obstruction. Under anesthesia or heavy sedation, the veterinarian typically passes a urinary catheter through the urethral opening to flush the blockage back into the bladder, where it can be managed more safely.

In some male cats, especially those with repeated urethral blockages, veterinarians may recommend a surgical procedure called a perineal urethrostomy (PU). This surgery shortens and widens the urethral opening, making it more difficult for stones or plugs to cause a complete blockage in the future.

Why Water Is Your Cat’s Best Defense

Because urinary stones tend to recur, long‑term prevention at home is essential. Among all preventive strategies, promoting good hydration is one of the most effective.

Pet parents can:

• Offer fresh water in multiple locations around the home
• Use wide, shallow bowls made of ceramic or stainless steel, which many cats prefer
• Try pet water fountains, which encourage drinking through movement and sound
• Incorporate wet food into the diet to increase total water intake
• Add small amounts of water or broth (without salt, onions, or garlic) to food, if your veterinarian approves

For cats that have already experienced urinary stones, many veterinarians recommend water with lower mineral content (lower hardness) to help reduce the mineral load in the urine.

Diet also plays a central role. There are specialized urinary health diets formulated to help control urine pH and mineral levels. These diets are often labeled for pH control or urinary care and are available through veterinarians and reputable pet retailers. If your cat has a history of stones, ask your veterinarian which specific diet is most appropriate.

Regular moderate exercise is another valuable tool. Activity can encourage cats to drink more, support a healthy body weight, and stimulate more frequent urination. Interactive play sessions with wands, toys, or food puzzles can make movement fun and mentally enriching.

Finally, never underestimate the importance of healthy litter box habits. Cats are extremely clean animals, and many will avoid using a dirty or unpleasant litter box. Holding urine for long periods can contribute to urinary problems.

Experts commonly recommend:

• Keeping litter boxes very clean, scooping at least once or twice daily
• Providing at least two litter boxes for a single cat, and one additional box for each extra cat
• Placing boxes in quiet, low‑stress areas where the cat feels safe

By making it easy and comfortable for your cat to urinate whenever they need to, you help protect their urinary tract.

Partnering With Your Cat for Lifelong Urinary Health

Urinary stones can be challenging to treat and have a frustrating tendency to recur, but pet parents are not powerless. By recognizing early warning signs, prioritizing hydration, feeding an appropriate diet, and maintaining a clean, stress‑free litter box environment, you can dramatically lower your cat’s risk.

If you ever notice changes in your cat’s urination habits, such as straining, frequent trips to the litter box, blood in the urine, or accidents outside the box, contact your veterinarian promptly. Quick action can mean the difference between a manageable problem and a life‑threatening emergency.

With informed, proactive care, pet guardians can play a crucial role in protecting their cats from urinary stones and supporting comfortable, healthy lives for years to come.