Low-Carb Dieting and Urine: Why Your Urine Smells
Diet & NutritionDiet Types

Why Does a Low-Carb Diet Make Your Urine Smell Bad?

Why Does a Low-Carb Diet Make Your Urine Smell Bad?
Daoyang Naotou/Getty Images
By
Jody Braverman, CPT, FNS, RYT
Updated on August 6, 2025
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A major change in your diet, such as severely restricting carbs, can mean your body uses fat for fuel instead of glucose.

The breakdown of your body fats can cause your body to produce ketones, which may give the urine an unappealing odor. In turn, this triggers a series of symptoms, including urine that smells strange.

Low-Carb Diets Explained

“Low-carb diet” is a very broad term. It encompasses different dietary patterns that all focus on the intake of fewer carbs than the recommended adequate intake of 275 grams (g) a day.

That’s a wide spectrum. A low-carb diet could include 100 g of carbs per day, or it could include much less. A typical limit may be 20 to 57 g carbs daily.

A moderate low-carb diet shouldn’t cause any major side effects — maybe some fatigue and weakness.

Very low-carb diets, such as the popular ketogenic diet, are more likely to cause noticeable symptoms, such as:

  • Fatigue
  • Vomiting
  • Nausea
  • Diarrhea
  • Dizziness
  • Headache
  • Reduced tolerance to exercise
  • Insomnia
  • Muscle cramps
  • Skin rash
Bad breath is another common symptom of very low-carb diets.

The odor is often described as “fruity,” but not in a good way.

Although not as common, excessive ketones in the bloodstream can mean your sweat and urine may have a similar odor.

Why Does Ketosis Make Urine Smell?

When you severely restrict carbs, you deprive your body of its primary energy source, and it has to find alternate fuel.

This facilitates a natural metabolic process called ketosis, in which the body breaks down fatty acids to produce substances called ketones. It can then use these for energy.

There are three types of ketone bodies present in the blood in ketosis: acetoacetate, beta-hydroxybutyrate, and acetone. Acetone is responsible for the fruity odor.

 People often describe the odor as smelling like nail polish remover, which often contains acetone as a solvent.

The higher the concentration of ketone bodies in the blood, the more pungent the smell is likely to be.

In people with diabetes, especially those with type 1 diabetes, a fruity odor to the breath can be a sign of a serious condition called diabetic ketoacidosis (DKA). In DKA, ketones build up to dangerous levels.

Nutritional ketosis and DKA are not the same thing. In nutritional ketosis, you only produce moderate amounts of ketones that don’t affect the pH, or acidity, of the blood.

DKA, on the other hand, is a life-threatening emergency. It can increase the blood’s pH through the excessive buildup of ketones.

A well-managed, low-carbohydrate diet should not cause ketoacidosis. Rates of ketosis-linked illness are generally low in people following this type of eating plan.

Getting Rid of Urine Odor During a Low-Carb Diet

The easiest way to fix the keto urine smell is to add more carbs back into your diet and get out of ketosis.

But if you’re committed to a keto lifestyle and you’re going to stick it out, there may be a few tweaks you can make to your diet to reduce the odor.

Reduce Your Protein Intake

If you get your macros wrong and eat too much protein, it can make the smell worse. This is because your body produces ammonia during the breakdown of protein.

 Ammonia combined with acetone makes for some particularly strong breath and urine.

According to Sherrie Sonomura, RD, a Honolulu-based registered dietitian, certified diabetes care and education specialist, and certified health and wellness coach at Nourish, the keto diet typically contains 20 percent protein.

The keto diet is not a high-protein diet, but people often eat more protein than they should and not enough fat. Make sure you’re getting enough, but not too much.

Stay Hydrated

Diets, in general, can cause a lot of water loss, especially in the beginning.

 But low-carb diets can be especially dehydrating. They can even lead to emergency room visits for dehydration treatment.

You can tell when you’re dehydrated by looking at the color of your urine. When your hydration is on point, your urine should be a light straw color. Dark yellow or orange urine points to dehydration.

 It may also have a stronger smell because it’s more concentrated.

On a keto diet, drinking water and other unsweetened beverages should be like a second job.

If you get dehydrated, in addition to dark urine, you may also feel tired, dizzy, and thirsty — even more than the usual “keto flu” symptoms.

If you’re also having low-carb-diet-related problems with smelly breath, the dry mouth that dehydration causes can worsen them.

You probably need to drink more than you think. Females need 11.5 cups of fluids a day, and males should drink 15.5 cups of fluids per day. Some of that comes from your diet, but the lion’s share should come from fluids.

Other Reasons for Urine Odor Changes

If your urine doesn’t have the characteristic keto urine smell, and your breath doesn’t also smell, you may want to consider other reasons for your smelly pee.

Even in the absence of ketones, being dehydrated can lead to smelly urine, so be sure to drink plenty of fluids.

Certain foods and beverages can make urine smell more pungent, including asparagus, fish, garlic, and onions. Certain vitamins, such as vitamins B and D, and medications, like sulfonamide antibiotics, diabetes medications, or sulfasalazine, can also lead to a more distinct urine smell.

Some medical conditions can also cause a change in urine odor, such as:

  • Yeast infections, due to the mixing of urine with vaginal discharge
  • Some sexually transmitted infections (STIs), again due to combination with discharge
  • Kidney stones, due to excess ammonia and salt
  • Poorly managed diabetes, as blood sugar can give urine a sweet smell
  • Urinary tract infections (UTIs), resulting from bacterial growth
It’s always a good idea to consult your doctor before starting a low-carb diet or carrying out any type of significant diet change.

While fruity-smelling pee is a normal side effect of slightly increased ketones, ruling out underlying health causes can help you prevent complications and maintain peace of mind.

The Takeaway

  • A very low-carb diet, such as the ketogenic diet, can cause an unusual urine odor due to the production of ketones, specifically acetone, as the body burns fat for energy.
  • If you’re experiencing strong-smelling urine on a low-carb diet, staying hydrated and managing your protein intake may help reduce the odor.
  • Health conditions, such as poorly managed diabetes and infections, might also cause changes in your urine smell. Consult a healthcare professional if you notice persistent or new symptoms.
  • While nutritional ketosis is typically safe, vigilant monitoring and balanced dietary choices are crucial to avoid potential health issues associated with extremely low carbohydrate intake.
EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
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Kara-Andrew-bio

Kara Andrew, RDN, LDN

Medical Reviewer
Member of American College of Lifestyle Medicine

Kara Andrew, RDN, LDN, is the director of health promotion for Memorial Hospital in Carthage, Illinois. She is also licensed as an exercise physiologist and certified in lifestyle medicine by the American College of Lifestyle Medicine. Her experience includes corporate wellness, teaching for the American College of Sports Medicine, sports nutrition, weight management, integrative medicine, oncology support, and dialysis.

She earned her master's in exercise and nutrition science at Lipscomb University.

Andrew has served as a president and board member of the Nashville Academy of Nutrition and Dietetics. She was recently elected a co-chair of the fitness and medicine group in the American College of Lifestyle Medicine.

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Jody Braverman, CPT, FNS, RYT

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