Strong-smelling urine in older adults usually comes down to concentrated urine from not drinking enough fluids, but it can also signal a urinary tract infection, medication side effects, or less commonly, an underlying organ problem. In most cases, the cause is identifiable and manageable once you know what to look for.
Dehydration Is the Most Common Cause
As people age, their sense of thirst becomes less reliable. Research on adults over 65 shows they have a higher baseline concentration of dissolved particles in their blood, which essentially raises the threshold before their brain registers thirst. Under normal daily conditions, most independent older adults drink enough. But when challenged by heat, physical activity, or even just a busy day where they forget to drink, they experience noticeably less thirst than a younger person would in the same situation. Full fluid restoration eventually happens, but it’s slower.
This matters because when the body is even mildly dehydrated, the kidneys conserve water by producing more concentrated urine. That concentrated urine contains higher levels of urea and other waste products in a smaller volume of water, which intensifies the smell. The color deepens too, shifting from pale yellow toward amber or dark gold. European nutrition guidelines recommend about 1.6 liters of fluids per day for women and 2.0 liters for men (not counting water from food). For older adults who aren’t hitting those numbers, concentrated, strong-smelling urine is often the first visible sign.
If you’re caring for an older person, the practical fix is making fluids available and visible throughout the day rather than relying on them to feel thirsty. Water, tea, broth, and water-rich fruits all count. Certain conditions like heart failure or kidney disease may require fluid restrictions, so any changes should fit within existing medical guidance.
Urinary Tract Infections
UTIs are one of the most suspected causes of foul-smelling urine in older adults, and for good reason. Bacteria in the urinary tract break down urea into ammonia and other compounds, producing a noticeably unpleasant odor. Some of the bacteria most associated with this process, including Proteus mirabilis and certain strains of E. coli, use an enzyme called urease to convert urea into ammonium ions, which makes the urine more alkaline and intensifies the smell.
Here’s where it gets complicated. In younger adults, a UTI typically comes with burning during urination, urgency, and pelvic discomfort. In older adults, especially those in nursing homes, these classic symptoms are often absent or misleading. Instead, the signs may be a change in mental status, new confusion, behavioral changes, or a fall. One study found that using urine odor alone to identify UTIs in elderly nursing home residents led to an incorrect conclusion in roughly one third of cases. The smell can be misleading because many older adults carry bacteria in their urine without having an actual infection.
This condition, called asymptomatic bacteriuria, is remarkably common. Prevalence runs between 25% and 50% among nursing home residents, compared to about 4% of older adults living independently in the community. Asymptomatic bacteriuria is generally considered a benign, transient condition that doesn’t need treatment with antibiotics. Treating it unnecessarily can contribute to antibiotic resistance without providing any benefit.
A true UTI requires both bacteria in the urine and symptoms. Diagnostic criteria used in nursing homes call for a combination of findings: a change in urine character (color, odor, or sediment), along with other signs like fever, new confusion, or changes in urination patterns. If the only change is smell with no other symptoms, it’s less likely to be a true infection.
Medications, Supplements, and Diet
Several medications commonly prescribed to older adults can change the way urine smells. B vitamins, particularly B6, are well known for giving urine a strong, almost sulfur-like odor. Certain antibiotics can do the same. Even asparagus, garlic, and coffee can temporarily alter urine odor through compounds that get filtered by the kidneys.
Because older adults often take multiple medications at once, pinpointing which one is responsible can take some detective work. If a new smell appeared around the same time as a new prescription or supplement, that’s a strong clue. The odor from medications and supplements is harmless and typically resolves when the substance clears the body.
Incontinence Products and Hygiene
For older adults who use absorbent pads or briefs, the smell you notice may not reflect what’s happening inside the body at all. Research into the odor chemistry of used incontinence products found that the smell is caused by far more than just the urine itself. When an absorbent product sits against the skin, it comes into contact with perspiration, skin bacteria, vaginal or urethral discharge, and sometimes fecal traces. Over time, bacteria on the skin metabolize these substances and generate volatile compounds that produce a strong, distinctive odor.
This means a product that smells intensely after several hours of wear doesn’t necessarily indicate a medical problem. More frequent changes, gentle cleansing of the skin at each change, and barrier creams can dramatically reduce both odor and the risk of skin breakdown. If the smell is present in freshly voided urine before it contacts any product, that points more toward a body-level cause like dehydration or infection.
Liver and Kidney Problems
Less commonly, persistently strong urine odor in an older adult can reflect a problem with the liver or kidneys. The liver is responsible for converting ammonia, a toxic byproduct of protein metabolism, into urea so the kidneys can safely excrete it. When the liver is damaged, as in cirrhosis, ammonia levels in the blood can rise. Cirrhotic liver disease accounts for about 90% of cases of elevated ammonia in adults. This can give urine (and sometimes the breath and sweat) a sharp ammonia-like smell.
Kidney disease can also concentrate waste products in the urine or alter the body’s ability to filter and dilute properly. A sweet or fruity urine smell in someone not known to have diabetes could indicate uncontrolled blood sugar, which is worth checking, since diabetes prevalence increases with age and can go undiagnosed.
When the Smell Signals Something Serious
A temporary change in urine odor after eating asparagus or starting a new vitamin is nothing to worry about. Persistent changes deserve attention, especially when combined with other symptoms. In older adults, the combination of foul-smelling urine with any of the following warrants a closer look:
- New confusion or agitation, which is the most commonly reported sign of UTI in nursing home residents, appearing in about 39% of suspected cases
- Fever or chills, present in roughly 13% of suspected UTI cases in this population
- Visible blood in the urine or a significant change in color
- New incontinence or changes in urination patterns
- Falls or sudden changes in walking, reported in nearly 9% of suspected UTI presentations
A urine dipstick test can check for white blood cells and nitrites as an initial screening step. If both are negative, a UTI is much less likely, and the smell probably has a simpler explanation. If symptoms are present alongside the odor change, a urine culture can identify whether bacteria are present in meaningful numbers and, if so, which antibiotic will work.