What Does It Mean When the Vet Says My Dog Has Crystals in Her Urine?

November 02, 2026 • After the Vet Visit • All Posts • Bladder Stones • Dogs • Health & Wellness • Urinary Health

By Theresa Gibilisco, owner, The Hungry Puppy

"We found crystals in her urine." It's a short sentence, and it can leave you picturing something painful and sharp inside your dog. People bring this one to our counter a lot, often along with a new prescription food and a question about whether their dog is going to need surgery. The honest answer is that it depends on what kind of crystals they are, and whether there are stones too.

Here's what the words mean, what usually happens next, and what it means for feeding at home, based on what the veterinary manuals and specialists say. It's general information. Your vet has the final word on your dog's care.

What does it mean when a dog has crystals in her urine?

It means tiny mineral particles showed up when the vet looked at a urine sample under a microscope. The medical word is crystalluria. Crystals are not the same as stones. Cornell explains that crystals can stick together and grow into stones (uroliths), but the Merck Veterinary Manual is clear that crystals alone do not mean your dog has stones, and stones can be there without crystals.

Do crystals always need treatment?

Not always. VCA says crystals in the urine "do not always indicate disease," and Merck notes that microscopic crystals seldom cause signs on their own. Crystals can even form in the cup after the sample is collected, as it cools or waits to be tested. Those don't matter, which is why vets prefer to look at a fresh sample. Your vet may want to recheck a fresh sample, take an X-ray or run a culture before deciding anything.

Words you might hear

Crystalluria: crystals in the urine.
Urolith: a stone in the urinary tract, such as a bladder stone.
Struvite: a crystal or stone made of magnesium ammonium phosphate.
Calcium oxalate: another common crystal or stone type, which behaves very differently from struvite.
Urine pH: how acidic or alkaline the urine is. Diet can shift it.
Urine specific gravity (USG): how concentrated or watery the urine is. For stone prevention, more watery is the goal.
UTI: a urinary tract infection, usually a bacterial bladder infection, confirmed with a urine culture.
Cystocentesis: collecting urine with a sterile needle straight from the bladder. It's the cleanest sample.

What's the difference between struvite and calcium oxalate?

They're the two most common stone types in dogs, per Merck, and they're managed in nearly opposite ways.

	Struvite	Calcium oxalate
Forms in urine that is	Neutral to alkaline	Acidic and concentrated
Usual cause in dogs	Bladder infection	Varies; vets look for underlying causes
Can stones dissolve with diet?	Usually, yes	No
Diet's job	Dissolve, then help prevent	Help prevent new stones

What does struvite mean for my dog?

In dogs, struvite usually goes hand in hand with an infection. Merck says most canine struvite stones form along with urinary infections caused by bacteria that make an enzyme called urease, and those bacteria can make the urine alkaline, which helps struvite form. Struvite without infection is rare in dogs. Cornell says struvite stones are more common in young, female, small-breed dogs, though any dog can get them.

The usual treatment is an antibiotic plus a prescription dissolution diet. These diets are lower in magnesium, phosphorus and protein, and they help make the urine more acidic and more dilute, according to Cornell.

How long does it take? Sources give slightly different timeframes:

Merck: complete dissolution takes 1 to 2 months on average, sometimes longer, with a recheck at about 4 weeks.
Cornell: dissolution can be effective in 8 to 12 weeks or sooner, with urine rechecks along the way and X-rays about every four weeks.

Merck adds that stones that haven't shrunk after 1 to 2 months probably aren't struvite.

The diet has to be the only food. Merck and VCA say a dissolution diet is fed with no other food or treats. VCA specifically says no treats or supplements. Even a little extra food can work against it.

After the stones are gone: sources differ. Merck says a long-term special diet isn't needed once the infection has cleared, while Cornell says most dogs need lifelong management to keep stones from coming back. Your vet will decide which fits your dog. Everyone agrees on preventing repeat infections and getting more water in.

What does calcium oxalate mean for my dog?

It means the stones can't be dissolved with food. The American College of Veterinary Internal Medicine (ACVIM) consensus statement and Merck both say calcium oxalate stones can't be dissolved medically, so the stones have to be physically removed by your vet.

Merck lists Miniature Schnauzers, Chihuahuas, Bichons, Yorkies, Shih Tzus and Lhasa Apsos among the small breeds at higher risk, and says these stones tend to form in middle-aged to older dogs, though young dogs can get them too.

Diet then focuses on keeping new stones from forming. Merck says to expect them to come back and suggests imaging every 3 to 6 months for high-risk dogs. Prevention usually means:

Wet food. The Minnesota Urolith Center recommends canned therapeutic food or added water to keep the urine dilute. ACVIM recommends foods that are more than 75% water, or water added to kibble.
No urine acidifying. ACVIM says diets and medicines meant to make the urine acidic should be avoided for these dogs, so the struvite approach is the wrong one here.
Skipping certain extras. A Minnesota Urolith Center handout says to avoid calcium supplements given apart from meals and high-oxalate foods such as nuts, rhubarb, spinach and chocolate (which dogs shouldn't have anyway).

Your vet may also prescribe a urinary prevention diet or a medicine to adjust the urine.

Why does water matter so much?

Watery urine makes it harder for minerals to come together. The ACVIM consensus cites short-term studies in which high-moisture food lowered a lab measure of oxalate stone risk in dogs, and Cornell recommends canned food or water added to dry food to help prevent struvite too. Keep fresh water out all day, and ask your vet whether wet food makes sense for your dog.

When is it an emergency?

A dog straining to pee with little or nothing coming out needs to go to your vet or an emergency clinic now. VCA warns that stones can block the urethra, the tube urine leaves through, and that complete blockage is life-threatening. It's more common in male dogs, whose urethra is longer and narrower, and the risk remains while a struvite stone is still dissolving.

What about cats with crystals?

Cats are a different story, so here's the short version:

Crystals alone often need no treatment. Merck says struvite crystals occasionally show up in healthy cats without stones and don't necessarily need treatment. VCA says many cases are an incidental finding that needs no treatment.
A common cause of urinary signs is feline idiopathic cystitis (FIC), painful bladder inflammation with no single known cause. "Idiopathic" means no known cause. International Cat Care says it is not an infection and should not be treated with antibiotics, and that conflict with another cat in the house is the most common source of stress in cats with FIC.
Wet food and more water help. Cornell recommends wet food make up at least 50% of a cat's diet to help prevent stones. For cats with a struvite history, Cornell says not to add urine acidifiers on top of a urinary diet.
A blocked male cat is an emergency. Merck says male cats are uniquely prone to a plugged urethra. A cat going back and forth to the litter box, crying, and passing little or no urine can look constipated. Cornell calls this "an absolute emergency" and warns that death may come in less than 24 to 48 hours after the bladder is completely blocked. Go to your vet or an emergency clinic now.

What questions should I ask my vet?

What type of crystals are they? Are there stones, too?
Was the sample fresh? Should we recheck it?
Is there an infection? Will you culture the urine?
If it's struvite, how long will dissolution take, and when are rechecks?
Can she have any treats while on the diet?
After this, does she need a prevention diet long term?
What signs mean I should come in right away?

Where to go from here

For a broader look at how prescription and therapeutic foods are built, read special diets for dogs and cats: what the food should look like. If your vet also mentioned your dog's weight, see what it means when the vet says my dog is overweight. For cats with kidney values flagged on the same bloodwork, see what it means when the vet says my cat has kidney disease.

Prescription diets need your vet's authorization, and we're happy to reach out to your vet for you through our prescription diets service. Our own trucks deliver free on each town's route day, Tuesday through Friday, with a $20 minimum. Find your day on our local delivery page, or call 732-938-4470. For a sit-down conversation about your pet's food, book a free 45-minute Personal Pet Consultant appointment.

Sources

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