Does a High Protein Diet Change the Smell of Urine?

October 20, 2025 •

4 min read

According to urologists, a change in urine odor is a common and often harmless side effect of a high protein diet. This phenomenon is typically linked to the body's metabolic processes as it breaks down protein and fat for energy, leading to the excretion of specific compounds in the urine. Understanding the science behind this can help demystify why your bathroom habits may be slightly different on this eating plan.

Quick Summary

A high protein diet can lead to a noticeable change in urine smell due to increased production of ammonia and ketones. The body converts excess protein into urea, which is then excreted. Insufficient hydration can concentrate these compounds, intensifying the odor. Managing this involves proper hydration and potentially adjusting protein intake.

Key Points

Ammonia and Urea Production: A high protein diet increases metabolic byproducts like urea and ammonia, which can give urine a stronger, more pungent smell.
Ketosis and Sweet Odor: For those on low-carb, high-protein plans, the body burns fat for fuel, producing ketones that can give urine a sweet or fruity scent.
Dehydration is Key: Insufficient water intake concentrates waste products in urine, intensifying any odor present from diet or other factors.
Diet and Supplements Matter: Specific foods (like asparagus, garlic) and B-vitamin supplements can contribute to stronger or different smelling urine.
Hydration is the Solution: The most effective way to manage and mitigate urine odor from a high protein diet is to increase your daily water intake.

The Science Behind Urine and Protein

Urine is a waste product filtered by the kidneys, and its composition is a direct reflection of what you consume and how your body is functioning. On a typical diet, the body primarily uses carbohydrates for energy. When you significantly increase your protein intake, especially while restricting carbohydrates (like in a ketogenic or very low-carb diet), your body's energy source shifts.

The Role of Ammonia and Urea

One of the primary reasons a high protein diet can alter urine odor is the metabolic byproduct of protein: ammonia. When the body breaks down protein, the nitrogen is converted into ammonia and then into a less toxic substance called urea by the liver. This urea is carried by the bloodstream to the kidneys and excreted in the urine. While urea itself is odorless, if you are consuming a very large amount of protein, the increased concentration of this waste can cause a stronger, sometimes ammonia-like, smell.

The Influence of Ketosis

For those on very low-carbohydrate, high-protein diets, the change in urine odor is often linked to ketosis. When carbohydrate intake is low, the body enters a metabolic state where it burns fat for fuel, producing compounds called ketones. Acetone is one type of ketone that can be excreted in the breath and urine, giving it a distinctive sweet or fruity smell, which some people might perceive differently, even like popcorn.

Factors Amplifying Urine Odor

Dehydration

One of the most significant factors influencing urine smell on any diet is hydration. When you are dehydrated, your urine becomes more concentrated because there is less water to dilute the waste products. This means the ammonia and other compounds are present in higher concentrations, leading to a much stronger and more pungent odor. A high protein intake requires more water for the kidneys to properly filter the waste products, making proper hydration even more critical.

Specific Foods and Supplements

Beyond just the macronutrient ratio, certain foods and supplements can have a direct impact on urine odor. These include:

Asparagus: Contains asparagusic acid, which produces sulfur-containing byproducts after digestion.
Garlic and Onions: Rich in sulfur compounds, which can also be excreted in urine.
Coffee: Certain metabolites from coffee can be detectable in urine.
Vitamin B supplements: Water-soluble vitamins like those in B-complex can cause a stronger odor and a more vibrant yellow color in urine.

Comparison of High Protein Diet and Other Causes


Cause of Smelly Urine	High Protein Diet	Dehydration	Urinary Tract Infection (UTI)	Diabetes (uncontrolled)
Primary Mechanism	Increased urea and ammonia production from protein breakdown. Possible ketosis if low-carb.	Lack of water to dilute metabolic waste products.	Bacterial growth and infection in the urinary tract.	Excess sugar and ketones excreted in urine.
Common Odor	Ammonia-like or sweet/fruity (if in ketosis).	Strong, concentrated ammonia smell.	Foul, fishy, or pungent odor.	Sweet or fruity smell.
Other Symptoms	Typically none, or 'keto flu' symptoms.	Dark urine, thirst, fatigue, dizziness.	Burning sensation, frequent urination, cloudy urine.	Increased thirst, frequent urination, fatigue.
Management	Increase water intake, balance protein with other macronutrients.	Drink more water and other fluids.	Antibiotics prescribed by a doctor.	Medical management of blood sugar levels.

How to Manage Changes in Urine Odor

If you're noticing a change in urine odor on a high protein diet and it's not accompanied by other worrying symptoms, there are several simple steps you can take to manage it:

Prioritize Hydration: This is the most effective solution. Drinking plenty of water helps dilute the concentration of waste products, normalizing the odor.
Assess Protein Intake: While high protein is the goal, ensure it's not excessively high for your activity level. A balanced approach can prevent the body from producing excess urea.
Balance Macronutrients: Ensure your diet isn't overly restrictive in carbohydrates. A balanced macronutrient ratio can prevent significant ketone production.
Dietary Adjustments: If specific foods like coffee or supplements seem to be a factor, consider temporarily reducing or eliminating them to see if the odor improves.

When to Seek Medical Advice

While a changed urine odor due to a high protein diet is usually harmless, it's important to be aware of the signs that may indicate a more serious underlying health issue. You should consult a healthcare professional if the smelly urine persists or is accompanied by other symptoms, such as:

A burning sensation or pain during urination.
Cloudy or dark-colored urine.
Increased frequency or urgency of urination.
Unusual fatigue or fever.

Conclusion

In summary, a high protein diet can indeed change the smell of urine, and it's a common and expected side effect for many people. The change is primarily caused by the metabolic processes that produce ammonia and urea from protein, which become more concentrated when dehydrated or in a state of ketosis. By focusing on adequate hydration, monitoring protein levels, and balancing your overall macronutrient intake, you can effectively manage and reduce this effect. However, always pay attention to your body and consult a healthcare provider if the odor persists or other concerning symptoms arise, as it could signal a different health issue.

Mayo Clinic's overview on the causes of urine odor provides additional context for those concerned about their symptoms.

Frequently Asked Questions

Your urine may smell like ammonia on a high protein diet because your body is converting excess protein into urea, which is then excreted by your kidneys. If you are also dehydrated, the concentration of these waste products will be higher, amplifying the ammonia-like odor.

Sweet-smelling urine on a high protein diet is often a side effect of ketosis. When you restrict carbohydrates, your body burns fat for energy, producing ketones. One of these, acetone, is excreted in urine and can cause a sweet or fruity scent.

The most effective way to reduce urine odor is to increase your water intake. Proper hydration helps dilute the waste products from protein metabolism. You can also try balancing your macronutrient ratios to ensure you are not overly restricting carbohydrates.

In most cases, a changed urine odor due to a high protein diet is harmless and temporary. However, if the odor is accompanied by other symptoms like pain, fever, or cloudy urine, you should consult a doctor, as it could indicate an underlying health issue like a UTI or uncontrolled diabetes.

No, not all high protein diets cause a noticeable change in urine odor. The effect is often more pronounced on very low-carb, high-protein plans (like keto) or if a person is not drinking enough water. Individual body chemistry can also play a role.

Yes, some supplements, particularly B-complex vitamins, are known to cause a stronger, sometimes medicinal, smell in urine. Since these are water-soluble, they are often excreted in the urine.

On a high protein diet, dehydration causes urine to become more concentrated with metabolic waste products like urea and ammonia. This lack of dilution makes the urine darker in color and gives it a more potent, stronger smell.