Fishy-smelling urine in dogs usually points to one of a few common issues: a urinary tract infection, anal gland problems, or, in female dogs, a reproductive tract infection. The smell itself comes from bacteria or bodily fluids that produce sulfur- and nitrogen-based compounds, and it’s almost always a sign something needs attention rather than a normal variation in your dog’s scent.
Urinary Tract Infections Are the Most Common Cause
A urinary tract infection is the first thing to consider when your dog’s pee takes on a strong, fishy odor. Bacteria colonize the bladder or urethra, multiply in the urine, and produce waste products that give off that unmistakable smell. The most common culprit is E. coli, a fecal bacterium that migrates into the urinary tract, though several other bacterial species can do the same thing.
UTIs are surprisingly common. Among dogs showing lower urinary tract symptoms, roughly 45% test positive for a bacterial infection. Females are significantly more prone than males, with about twice the infection rate, because their shorter urethra gives bacteria a shorter path to the bladder. But males, puppies, and senior dogs all get them too.
Beyond the smell, watch for frequent urination, straining to pee, accidents in the house, cloudy or dark urine, and licking around the genital area. Some dogs show no obvious discomfort at all, and the odor is the only early clue. Healthy dog urine typically falls within a pH range of 5.0 to 7.5. When infection shifts that balance, it can create conditions where bacteria thrive even more aggressively, intensifying the smell over time.
Anal Glands Can Fool You
Here’s something many dog owners don’t realize: that fishy smell might not be coming from the urine at all. Dogs have two small scent glands located just inside the rectum, and when those glands become clogged, inflamed, or overly full, they release a potent, fish-like secretion. Because the fluid can leak onto the fur around your dog’s back end, it’s easy to notice it during or after urination and assume the pee itself is the source.
Anal glands normally express small amounts of fluid during bowel movements. It’s part of how dogs mark territory and identify each other. Problems start when the ducts that drain these glands get blocked. Fluid builds up, thickens, and the smell becomes far stronger than usual. Left untreated, impacted glands can become infected or develop into painful abscesses. Signs of anal gland trouble include scooting along the floor, excessive licking under the tail, and visible swelling or redness near the anus.
If you’re noticing the fishy smell mostly when your dog sits down, scoots, or licks their rear rather than specifically during urination, anal glands are the more likely explanation. A vet or groomer can express impacted glands in minutes, and some dogs need this done regularly.
Reproductive Infections in Female Dogs
In unspayed female dogs, a fishy or foul smell near the urinary area can signal a uterine infection called pyometra. This is a serious condition where bacteria invade the uterus, causing it to fill with pus. Early signs are subtle: increased thirst, more frequent urination, and decreased appetite. In “open” pyometra, you’ll see vaginal discharge that ranges from thick and yellowish to bloody, and this discharge can easily mix with urine or drip in the same spot, creating the impression that the pee itself smells off.
Vaginitis, an inflammation of the vaginal lining, is another possibility. It’s more common in puppies and older dogs and produces a similar-smelling discharge. While vaginitis is usually less urgent than pyometra, both conditions need veterinary treatment. Pyometra in particular can become life-threatening if the infection spreads, so any unspayed female dog with foul-smelling discharge, lethargy, or loss of appetite should be seen promptly.
Diet and Dehydration Play a Role
Sometimes the explanation is simpler. Concentrated urine smells stronger across the board, so if your dog isn’t drinking enough water, their pee will have a more pungent odor. Certain fish-based dog foods can also change the scent of urine noticeably. This doesn’t mean you need to switch foods, but it’s worth noting whether the smell appeared around the same time as a diet change.
Asparagus, certain supplements, and high-protein diets can all alter urine odor in dogs, just as they do in humans. If your dog seems otherwise healthy, is urinating normally, and the smell is mild, try increasing their water intake for a few days and see if the odor fades. Persistent or worsening fishiness, though, warrants a closer look.
What a Vet Visit Looks Like
Diagnosing the cause is straightforward. A standard urinalysis examines the urine’s color, clarity, pH, and concentration, then checks for the presence of bacteria, blood cells, protein, glucose, and crystals. Your vet can run a dipstick test in the office within minutes. If bacteria are found, a urine culture identifies the exact species and which treatments will work against it, which takes a few days to come back.
For suspected anal gland issues, a physical exam is usually all that’s needed. For female dogs with discharge, imaging or blood work may be added to check for pyometra.
Signs That Need Urgent Attention
Most causes of fishy-smelling urine are treatable and not emergencies. But certain combinations of symptoms signal something more serious. Straining repeatedly to urinate while producing little or no output can mean a urinary blockage, which is a genuine emergency. Bright red blood or visible clots in the urine also demand quick action.
Other red flags to watch for alongside the smell: vomiting, refusal to eat, extreme lethargy, crying or whimpering during urination, a tense or painful abdomen, pale gums, or collapse. Any of these paired with abnormal-smelling urine means your dog needs to be seen that day, not next week.