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What Are Ketones in Urine?

Published on: June 19, 2018

What Are Ketones in Urine?

What are ketones in urine? It's the presence of ketones in your urine due to high levels of ketone body production. Ketones can build up for several reasons, such as fasting, low carb diets, and diabetes [1]. The presence of ketones in a low carb diet like the keto diet is harmless and could indicate nutritional ketosis. Ketoacidosis, however, is not harmless, and could be life-threatening when not treated on time.

What Are Ketones in Urine?

Ketones in urine refer to the presence of high levels of ketone bodies in your urine. They’re metabolically active strong acids that your body uses for fuel when glucose is restricted. The three main types of ketones your body produces are acetoacetic acid, beta-hydroxybutyric acid, and acetone (least abundant). Ketones are always present in the blood, and their level can increase in different situations like prolonged exercise or fasting [2]. The presence of high levels of ketones in the urine is known as ketonuria.

The blood ketone level in healthy individuals is self-limited and harmless because insulin will be released when the concentration is at 2 to 4mM or higher. Insulin production will prevent ketoacidosis by restricting the production of ketones by the liver [3].

What Causes Ketones in Urine?

Your body can produce up to 300 g of ketones per day, and these ketones contribute to 5-20 % of energy expenditure in situations like fasting and starvation [4]. Here are some of the main causes of ketonuria (high ketones in urine).

Diabetic ketoacidosis

Ketones found in the urine of diabetic individuals could indicate Diabetic Ketoacidosis which refers to a dangerously high level of ketones in the blood. This could happen when the insulin level in the blood is too low to regulate blood glucose and limit fat from being broken down into ketones. DKA is a medical emergency that could be fatal when not treated on time [5].

Prolonged exercise

A 2017 research paper (ref 3) states that prolonged exercise can increase blood ketone levels up to ~1 mM. The ketone bodies can be used as fuel during and after post exercise, especially when the glucose level is low. The utilization of ketone bodies as fuel during and after exercise could vary in trained and untrained individuals [6].


Low carb diets

If you’re on a low carb diet like the ketogenic diet, your body will be using fat as its primary fuel source instead of glucose via a process called nutritional ketosis [7]. This is when fatty acids are converted into ketones to be used as fuel, and this can cause ketones to show in your urine. The ketone levels on a low carb diet don’t usually increase to a dangerous level like ketoacidosis discussed above.

Other causes of Ketones in the urine can include:

  • Chronic vomiting
  • Fasting
  • Eating disorders
  • Pregnancy
  • Certain medications and drugs
  • Excessive alcohol

How to Test for Ketones in Urine

You can use ketone test trips, also known as ketone urine tests to find out the presence and level of ketones in your urine. You can buy them online, or at your local pharmacy or supermarket but make sure to buy a reputable brand.

Most ketone urine strips require the following procedure [8]:

  1. Wash your hand and collect your urine sample in a small container.
  2. Dip the right end of the strip into the urine sample for a few seconds and then remove.
  3. Wait for the required time mentioned on the package for color changes.
  4. Compare your result with the color chart from your test package.
  5. Dispose of the strip and urine sample hygienically and wash your hands.

Other indications of high ketones can include frequent urination, extreme thirst, tiredness, shortness of breath, chronic vomiting, and sweet-smelling breath.

Ketone Urine Test Results & Interpretations

Ketone urine tests usually allow you to see your ketone level via a leveled colored chart that comes on their package. Each color indicates what level of ketones you may have in your body. The lighter end of the chart shows the lowest level of ketones, and the darker end means a higher level (ref 7). For example, the lightest shade could say negative, and the darkest could say high or large. The middle color stands for moderate, and that’s usually the one that indicates you could be in nutritional ketosis.

Best Time to Test Urine for Ketones?

One study investigated the best time to test for ketones in urine in 12 healthy participants. The participants were on the ketogenic diet for six weeks and achieved a stable ketosis state before they were asked to measure their ketone levels. Results revealed that the highest and reliable level of ketonuria was detected in the early morning and post-dinner urine. Consider taking your ketone urine test at these times for reliable results [9]. For accurate results, take your test at the same time every week and compare the results.

What Is a Good Urine Ketone Level for Ketosis?

The normal level of circulating ketones is less than 0.3mM. Anything between 0.5-3mM is considered to be the best ketone level for nutritional ketosis. Also, remember that the ketone level can vary throughout the day. E.g., circulating ketone levels can increase up to 5-10mM during prolonged fasting [10].

When Should I See a Doctor?

It’s important to keep an eye on your ketone level if any of the following applies to you:

  • You have high blood sugar
  • You’re an alcoholic
  • You have chronic diarrhea and/or vomiting
  • You’re pregnant
  • You’ve been fasting
  • You have an infection

If you’re not on a low carb diet like the ketogenic diet, you should see the doctor if you experience any of the symptoms of ketoacidosis. Some of which include fruit smelling breath, increased thirst, frequent urination, vomiting, and diarrhea. It’s even more crucial if you have high blood sugar, diabetes, or if you’re pregnant.


Ketones are always present in your blood in a small quantity, but their level can increase in different circumstances such as fasting, prolonged exercise, ketoacidosis, or during a low carb diet. Ketone urine tests are an easy and affordable way to test your ketone levels to determine if you’re in ketosis.


  • 5-3.0 mMl is considered to be the best ketone level for nutritional ketosis.
  • You can measure your ketone level using ketone urine strips and the best time to test is in the early morning or post-dinner.
  • Ketone levels can vary throughout the day depending on what you’re doing. E.g., ketone levels can increase during fasting and exercise.
  • Please go to your doctor right away if you experience any of the ketoacidosis symptoms we’ve discussed such as fruity breath, frequent urination, vomiting, and shortness of breath. Nutritional ketosis is safe, but ketoacidosis is a medical emergency.


  1. Newman JC, Verdin E. Ketone bodies as signaling metabolites. 2013 October 18 -
  2. Laffel L. Ketone bodies: a review of physiology, pathophysiology and application of monitoring to diabetes. 1999 November-December -
  3. Comstock JP, Garber AJ. Chapter 140... View all references

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