October 2026
Guinea pigs are talkers, so when yours lets out a sharp squeak every time they pee, it's worth paying attention. That squeak, along with blood in the urine or a sudden loss of appetite, is one of the classic signs of bladder stones. Stones are one of the most common urinary problems in guinea pigs, and one of the most frustrating, because they have a habit of coming back. Knowing the signs, and the steps that lower the risk, can make a real difference for your pig.
Stones form when minerals in the urine clump together into hard masses. In guinea pigs they're usually made of calcium. Most sit in the bladder, but they can also lodge in the kidneys, the tubes that carry urine, the urethra, or in males, a gland called the seminal vesicle.
We don't fully understand why some guinea pigs form stones and others don't. The likely contributors are a diet high in calcium (especially alfalfa or clover hay and high-calcium vegetables), mineral imbalances, not drinking enough water, genetics, and other urinary problems such as bladder infections or kidney disease. Irritation of the bladder lining may also set the stage for new stones.
It used to be thought that older females were most at risk. Newer evidence suggests males and females are affected about equally, and stones can show up at any age.
The most recognizable signs are squeaking or crying while urinating, straining or peeing small amounts often, and blood in the urine. In females it's important to tell urinary blood apart from bleeding from the reproductive tract, so mention it either way. Some pigs sit hunched or grind their teeth. And sometimes the only sign is eating less, especially when a stone is in the kidney or ureter.
A guinea pig, especially a male, who is straining and producing no urine may have a blocked urethra. That is an emergency.
X-rays usually show the stones. I make sure the entire back end is included, because stones stuck near the tip of the urethra are easy to miss. Ultrasound helps when it's unclear exactly where a stone is. A urine test and culture check for infection, and bloodwork looks at kidney function and overall health.
Most bladder stones need to be removed surgically, in a procedure called a cystotomy. I use specific surgical techniques chosen to help lower the chance of stones returning, and pain control and anti-inflammatory medication afterward keep your pig comfortable and may also calm bladder inflammation.
In some females, small stones near the opening of the urethra can be gently helped out without major surgery. When surgery isn't possible, care focuses on comfort and fluids.
For guinea pigs that have had stones, I often discuss long-term medication that helps reduce calcium in the urine and keep it dissolved, ideally started a few days before surgery and continued with regular bloodwork and urine checks.
Even after a successful surgery, stones return in a meaningful number of guinea pigs, often within months. That isn't a failure on your part. It's the nature of the disease. Repeat surgeries carry more risk, so prevention and monitoring really matter.
Diet is the place to start. Offer unlimited grass hay such as timothy rather than alfalfa or clover, a measured amount of plain guinea pig pellets with vitamin C, and daily vegetables leaning toward lower-calcium choices. I'm happy to help you build a list that suits your pig.
Water is just as important. Guinea pigs tend to drink more from bottles than bowls, so keep bottles clean and flowing, and consider adding a second one. Space and exercise encourage drinking and regular urination. For pigs with a history of stones, regular checkups and follow-up X-rays help us catch new stones while they're small.
Call immediately if your guinea pig is straining and producing no urine, has stopped eating, or is crying out, hunched and very quiet.
Book a prompt visit for blood in the urine, squeaking while urinating, frequent small urinations, or eating a little less than normal.
Dr. Logan Kopp, DVM, DABVP (Exotic Companion Mammal Practice), is Nashville's guinea pig specialist and performs bladder stone surgery and long-term stone prevention care at Priest Lake Veterinary Hospital. Call (615) 361-4646.
This article is general information, not medical advice for your pet. Reading it doesn't create a veterinarian-client-patient relationship (VCPR). Please talk with your own veterinarian before making changes to your pet's care.