Urine that smells like cat litter almost always comes down to ammonia. Your body naturally produces ammonia as it breaks down protein, and small amounts end up in your urine every day. Normally the concentration is low enough that you barely notice. When something shifts that balance, whether it’s dehydration, diet, an infection, or a hormonal change, the ammonia becomes concentrated or overproduced, and your bathroom starts smelling like a litter box.
Dehydration Is the Most Common Cause
When you don’t drink enough water, your kidneys have less fluid to dilute the waste products they filter out. The result is darker, more concentrated urine with a noticeably stronger ammonia scent. This is the single most frequent reason for a sudden change in urine odor, and it’s also the easiest to fix. Increasing your water intake over the course of a day usually resolves the smell within hours.
Holding your urine for long stretches compounds the problem. The longer urine sits in the bladder, the more time bacteria have to break down urea (a nitrogen compound your body excretes) into ammonia. That breakdown is the exact same chemical reaction that makes actual cat litter smell, since cat litter absorbs urea from cat urine and bacteria do the rest. If you regularly delay bathroom trips during a busy workday, you’re essentially recreating that process inside your own bladder.
High-Protein Diets Increase Ammonia Output
Protein metabolism generates nitrogen as a byproduct. Your liver converts that nitrogen into urea, which your kidneys then flush out. When you eat significantly more protein than your body needs, especially from animal sources, you produce higher levels of urea and other nitrogenous waste. Animal protein in particular generates more ammonia and sulfur-based compounds during digestion compared to plant protein. If you’ve recently started a high-protein or ketogenic diet and noticed the smell, this is likely the connection.
The fix doesn’t require abandoning the diet. Drinking more water helps your kidneys dilute the extra nitrogen. Balancing animal protein with some plant-based sources can also reduce the intensity of the odor.
Urinary Tract Infections
Many of the bacteria responsible for urinary tract infections are specifically equipped to break down urea into ammonia. Species like Proteus and Klebsiella carry an enzyme that lets them use urea as a nitrogen source, and in doing so, they flood your urine with ammonia. This raises the pH of your urine from its normal mildly acidic range (around 5.5 to 6.5) into alkaline territory, which intensifies the smell.
A UTI-related ammonia smell usually comes alongside other symptoms: burning during urination, a frequent urge to go, cloudy or discolored urine, or pelvic pressure. If you’re experiencing any of those alongside the cat litter scent, a simple urine test can confirm an infection. The test checks for bacteria, white blood cells, and nitrites, all markers of bacterial activity in the urinary tract.
Left untreated, certain ammonia-producing bacteria can also contribute to the formation of struvite kidney stones. These stones form when the ammonia from bacterial breakdown combines with minerals in your urine to create hard deposits. They’re more common in people with recurrent or chronic UTIs.
Hormonal Changes During Pregnancy and Menopause
Pregnancy can make you more sensitive to the faint ammonia smell that’s always present in urine. Heightened senses during the first trimester mean odors you previously ignored can suddenly seem overpowering. On top of that, pregnancy increases dehydration risk, and prenatal vitamins (particularly B vitamins) can alter urine odor on their own.
Menopause creates a different pathway to the same problem. As estrogen levels drop, the vaginal pH rises and the population of protective lactobacillus bacteria declines. This shift allows bacteria with the potential to cause urinary infections, like E. coli, to establish themselves more easily. The result is a higher rate of recurrent UTIs after menopause, which brings ammonia-producing bacteria into the urinary tract more frequently. If the cat litter smell keeps coming back and you’re in perimenopause or beyond, recurring low-grade infections may be the underlying cause.
Vitamins, Supplements, and Medications
B vitamins and vitamin D are well-known for changing the way urine smells. Since both are included in most multivitamins, starting a new supplement routine can produce a noticeable odor shift within days. The smell isn’t harmful in this case, just a side effect of your body excreting what it doesn’t absorb.
Certain medications also alter urine scent. Sulfa-based antibiotics, some diabetes medications, and rheumatoid arthritis drugs like sulfasalazine can all produce stronger or unusual urine odors. If the timing of the smell lines up with a new prescription, that’s worth noting.
When the Smell Signals Something Deeper
In rare cases, a persistent ammonia smell points to a problem with how your body processes nitrogen. Your liver is responsible for converting ammonia into urea so your kidneys can safely excrete it. When liver function is significantly impaired, this conversion becomes less efficient and ammonia can build up. Severe liver disease produces a distinctive sweet, musty odor on the breath and in urine caused by sulfur compounds that accumulate when the liver can’t keep up. This is quite different from a straightforward ammonia scent, but any persistent change in urine odor that doesn’t respond to hydration and dietary adjustments is worth investigating.
Kidney problems can also play a role. When the kidneys are under strain from chronic high-protein intake or existing kidney disease, they may struggle to handle the increased nitrogen load. Over time, this can worsen the ammonia concentration in urine and contribute to metabolic acidosis, a state where the body becomes too acidic and compensates by producing even more ammonia in the kidneys.
Practical Steps to Reduce the Smell
Start with hydration. Aim for enough water that your urine stays a pale yellow throughout the day. Dark yellow or amber urine is a reliable sign you need more fluid. This alone resolves the ammonia smell for most people.
If you’re eating a high-protein diet, try shifting some of your protein intake toward plant sources like lentils, beans, or tofu. You don’t need to reduce total protein dramatically, but the composition change reduces the ammonia and sulfur compounds your gut produces during digestion.
Don’t hold your urine for extended periods. Regular bathroom breaks prevent the bacterial breakdown of urea that intensifies the smell inside the bladder. If you’re also experiencing burning, urgency, or cloudiness alongside the odor, a urine test can quickly rule in or out a bacterial infection. For people going through menopause who notice the smell recurring, it’s worth checking whether low-grade UTIs are behind it, since they don’t always produce dramatic symptoms in postmenopausal women.