An unusually strong or foul-smelling odor coming from your senior dog’s urine can be alarming, especially when it appears suddenly or becomes worse over time.
While some changes in urine smell may be mild and temporary, others can signal underlying health issues that require immediate attention.
Old Dog Urine Smells Bad: Why It Happens
When an old dog’s urine smells bad, it is often caused by infections, dehydration, kidney problems, bladder disease, or metabolic conditions that change how waste is processed in the body.
As dogs age, their immune system and organ function gradually weaken, making them more vulnerable to bacterial growth, toxin buildup, and changes in urine concentration.
These internal shifts can cause urine to develop a sharp, ammonia-like, sweet, musty, or rotten odor.
In many cases, the smell reflects what is happening inside the urinary tract or bloodstream and should not be ignored, especially if it persists.
Old Dog Urine Smells Bad: Common Causes
Urinary Tract Infection (UTI)
Urinary tract infections are one of the most frequent reasons an old dog’s urine develops a strong, unpleasant smell. As dogs age, their immune defenses weaken, allowing bacteria to multiply more easily inside the bladder and urethra.
When bacteria grow in the urine, they produce waste products that create a sharp, foul, or ammonia-like odor.
Your dog may also urinate more often, strain while peeing, have accidents indoors, or lick their genital area excessively.
UTIs are serious in senior dogs because untreated infections can spread to the kidneys, bloodstream, or prostate, leading to more severe complications and long-term organ damage.
Related: Old dog smells bad (Here’s why)
Dehydration and Concentrated Urine
Older dogs are more prone to dehydration due to reduced thirst drive, kidney changes, or underlying illness. When a dog does not drink enough water, their urine becomes highly concentrated.
Concentrated urine contains higher levels of waste chemicals, which intensifies its natural smell. This often results in urine that smells very strong, sharp, or acidic.
You may notice darker-colored urine, smaller urine volumes, dry gums, fatigue, or decreased appetite. Chronic dehydration puts extra strain on the kidneys and bladder, increasing the risk of infections and kidney disease.
Kidney Disease
Chronic kidney disease is common in aging dogs and often causes noticeable changes in urine odor. As the kidneys lose their ability to filter waste effectively, toxins accumulate in the bloodstream and urine.
This buildup can give urine a strong ammonia-like, metallic, or chemical smell. Dogs with kidney disease may also drink more, urinate more frequently, lose weight, become lethargic, or develop bad breath.
Kidney disease is progressive and cannot be cured, but early treatment can slow its advancement and improve quality of life. A persistent urine odor may be one of the earliest warning signs.
Bladder Stones or Crystals
Bladder stones and urinary crystals form when minerals in the urine clump together. These structures irritate the bladder lining and can trap bacteria inside the urinary tract.
As inflammation and infection develop around stones, urine often becomes cloudy and foul-smelling. Some dogs may pass blood in their urine, cry while urinating, or suddenly refuse to pee.
This condition is dangerous because stones can block urine flow, causing life-threatening emergencies if not treated promptly.
Diabetes and Metabolic Disorders
Certain metabolic diseases, especially diabetes, can change how waste products are processed in the body. Diabetic dogs often have excess glucose in their urine.
This sugar-rich environment encourages bacterial growth and fermentation, leading to urine that smells sweet, fruity, or unusually strong. Increased thirst, increased urination, weight loss, and weakness often accompany these changes.
Other metabolic disorders can also alter urine chemistry, producing unusual odors that signal internal imbalance.
Hormonal and Age-Related Bladder Changes
As dogs grow older, hormone levels shift and bladder muscle tone weakens. These changes can interfere with normal urine storage and emptying.
Incomplete bladder emptying allows urine to sit longer inside the bladder, encouraging bacterial growth and waste buildup. Over time, this stagnant urine develops a stronger smell.
You may notice leakage during sleep, frequent dribbling, or difficulty holding urine.
While sometimes considered “normal aging,” these changes often require medical management to prevent complications.
Read more: Old Dog Farting A Lot (Hidden Health Causes)
Old Dog Urine Smells Bad: What to Do
If you notice a strong odor coming from your senior dog’s urine, begin by encouraging increased water intake. Offer fresh water frequently, clean bowls daily, and consider adding water or low-sodium broth to meals to promote hydration.
Monitor your dog’s urination habits closely. Pay attention to frequency, volume, color, and any signs of discomfort. Keeping notes can help your veterinarian identify patterns.
Maintain proper hygiene by cleaning your dog’s bedding and living areas regularly. This helps prevent bacterial buildup and allows you to better monitor urine changes.
Feed a high-quality, age-appropriate diet recommended by your veterinarian. Some prescription diets are specifically designed to support urinary and kidney health.
Avoid giving human medications or supplements without veterinary approval, as many substances can worsen kidney and bladder problems.
When to Call or Visit Your Veterinarian
Contact your veterinarian promptly if the urine odor lasts more than 24 to 48 hours, even if your dog seems otherwise normal.
Seek immediate veterinary care if your dog shows pain while urinating, blood in the urine, frequent accidents, or difficulty passing urine. These signs may indicate infection or obstruction.
Urgent attention is also needed if foul-smelling urine occurs alongside vomiting, weakness, appetite loss, increased thirst, or weight loss, as these may signal kidney disease or diabetes.
If your dog suddenly stops urinating, strains without producing urine, or cries while trying to pee, this is a medical emergency requiring immediate treatment.
Related: Old Dog Peeing All The Time (Warning Signs to Watch For)
Old Dog Urine Smells Bad: Treatment
Veterinary treatment for foul-smelling urine in an older dog focuses on identifying and treating the underlying cause, most commonly urinary tract infections (UTIs).
A veterinarian will typically perform a urinalysis and urine culture to detect bacteria, blood, crystals, or abnormal pH levels, and may also run blood tests to assess kidney function.
Treatment often includes targeted antibiotics, increased hydration, and sometimes prescription urinary diets to reduce recurrence.
If bladder stones, kidney disease, or tumors are suspected, imaging such as X-rays or ultrasound may be recommended.
Immediate treatment is important, as untreated urinary issues in senior dogs can quickly lead to pain, kidney damage, or systemic infection.
Key Takeaway
Bad-smelling urine in an old dog is never something to ignore, as it often reflects changes happening inside the urinary system or vital organs. Infections, dehydration, kidney disease, bladder stones, and metabolic disorders are among the most common causes.
With early veterinary care, proper hydration, and ongoing monitoring, many of these conditions can be managed successfully.
If your senior dog’s urine odor changes suddenly or becomes persistent, trust your instincts and seek professional guidance to protect their comfort and long-term health.