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March 25, 2021 / Brittany Cardwell, RDN, LD

How to Test for Ketones: Everything You Need to Know

Person pricking their middle finger to run a blood test to check for ketones.

Ketones, also known as ketone bodies, are produced by the liver and are always present in the blood to serve as an alternative energy source for the body when glucose is not readily available. The number of ketone bodies normally increases during times of fasting and prolonged exercise, however, there are other circumstances that can cause ketone levels to abnormally increase.

Testing for ketone levels is primarily advised for individuals with diabetes (more commonly type 1) who are at a higher risk of developing diabetic ketoacidosis (DKA). Ketone levels may also be monitored by those who are trying to reach a state of nutritional ketosis through a ketogenic diet. Although ketone testing is not required to follow a ketogenic diet, some people may find it helpful for tracking the effectiveness of their nutrition plan.

If you’re wanting to detect the presence of ketones in your body there are several at-home testing options available using urine, blood, or breath samples. In this article we’ll discuss how to test for ketones using each method and gain a better understanding of what the results mean.

What Are Ketones?

Ketones are produced during a process called ketogenesis, in which fat is broken down into fatty acids. This occurs when the main energy source for the body, glucose, is not readily available. For those with diabetes, ketones may also be produced if there is not enough insulin to utilize the glucose for energy.

The American Diabetes Association advises anyone with diabetes to check ketone levels after a blood sugar reading of more than 240 mg/dL. A ketone reading between 0.6 and 1.5 mmol/L is indicative of an increased risk of developing DKA. If a ketone level registers above 1.5 mmol/L, a medical provider should be consulted.

The goal of following a ketogenic diet is to reach a state of nutritional ketosis. Optimal ketone levels for this purpose are described by Dr. Stephen Phinney, MD, PhD and Jeff Volek, PhD, RD, authors of The Art and Science of Low Carbohydrate Living, as being between 1.0 mmol/L and 3.0 mmol/L.

Although both ketoacidosis and ketosis involve the production of ketones in the body, it’s important to note that they’re not the same. In those with insulin dependent diabetes, a ketone level above 0.6 mmol/L is abnormal and should be monitored. In comparison, for individuals on the ketogenic diet wanting to reach a state of nutritional ketosis, a ketone level above 0.5 mmol/L signals light ketosis.

Why Test Your Ketone Level?

When following a ketogenic diet, higher-than-normal levels of ketones indicates that carbohydrate intake is restricted enough to where the body is no longer using glucose as its primary energy source. Knowing how to test for ketones on a ketogenic diet helps measure progress and provides insight into how certain foods affect results. These ketogenic diet tips and consistent ketone testing are tools for reaching a state of optimal ketosis.

Ketone testing is also a key component to managing diabetes and preventing DKA, a life-threatening condition. This can occur in people with type 1 diabetes, or insulin-dependent type 2 diabetics when there’s an insufficient amount of insulin in the body to utilize glucose for energy. Risk for DKA also increases during serious illness when insulin doses are missed or not adjusted appropriately. As a result, the body starts breaking down fat for energy, producing ketones. If left untreated, ketone levels build up and can poison the body. Anyone with diabetes should discuss when to test for ketones with their physician.

What Are Some Physical Symptoms That You’re in Ketosis?

As the body begins to create a new fuel source for the cells in the form of ketones, you may notice some physical symptoms of ketosis, such as:

If your body is producing ketones you may experience any of the signs or symptoms listed above, however, a more accurate way in determining ketosis is to check for increased ketones in the blood, urine, or breath.

At-Home Ketone Test: Urine Test

One way to test for excess ketones is through a simple urine test. A urine test will show whether you have no ketones, trace amounts, moderate levels, or high amounts of ketones excreted in the urine. The results typically reflect a ketone level from a few hours prior. This can be done at-home with the use of special testing strips that change color when exposed to a urine sample. After an instructed amount of time, results are determined by comparing the color on the testing strip to the chart on the product’s packaging.

The best time to test for ketones in the urine is during the first few weeks of starting a ketogenic diet or anytime DKA is suspected in individuals with diabetes. Although urine testing is an easy and inexpensive way to screen for elevated ketone levels, it’s not considered the most accurate at-home testing method for measuring nutritional ketosis.

When should you test your urine for ketones?

When monitoring the effectiveness of a ketogenic diet, the best time to test for ketones in urine appears to be early morning or post dinner, according to one research study. Higher levels of ketones were noted to be more reliably detected during these time frames.

At-Home Ketone Test: Blood Test

The most accurate way to test ketone levels is through a blood test. Using a blood ketone meter, this test is carried out in a similar way to a blood glucose test. Instructions may vary depending on the device, but are typically carried out by inserting a blood ketone strip into the meter. From here, a small sample of blood is needed by pricking your finger with a lancing device. The drop of blood is then placed on the ketone strip for the meter to generate a reading. Compared to a urine test that measures the excess ketones that are excreted in the urine, a blood test measures the ketone body beta-hydroxybutyrate, which reflects the ketone level in your body at the moment of testing. A blood ketone reading may present as follows:

When performing an at-home blood test it is important to thoroughly read the testing kit instructions and to consult with your healthcare provider about what an optimal level is for you.

At-Home Ketone Test: Breath Test

A third at-home tool that can be used to test for ketones is a breath meter. Breath tests are used to analyze the amount of acetone in the breath, which is a byproduct of ketogenesis. For the most accurate and reliable results, a controlled, deep-breath should be taken into a ketone breath meter. According to this published review, breath acetone concentration levels (measured in parts per million) can correlate as follows:

This is a non-invasive ketone testing method, however, result accuracy will be affected by variable factors including environmental conditions and breathing techniques. Although there is a correlation between breath acetone and ketone production, it’s not the most accurate for measuring ketones as a result of DKA or nutritional ketosis.

What Should You Do If Your Ketone Levels Are Too High?

If you're following the ketogenic diet, the optimal zone for nutritional ketosis is 1.0 to 3.0 mmol/L. Ketone levels may be higher during times of fasting, or if consuming a much higher fat-to-protein ratio, however, this is not ideal unless following the diet under medical supervision for therapeutic purposes.

If you have diabetes, high levels of ketones and high blood glucose levels put you at risk for DKA. This is a serious health condition that requires immediate medical intervention. While waiting for guidance from a healthcare professional on how to treat high ketone levels, these steps may help in lowering your levels:

The Takeaway

Regardless of your reason for ketone testing, the most accurate measurement tool is a blood ketone test. Anyone with insulin-dependent diabetes needs to know when to test for ketones to minimize the risk of developing ketoacidosis. Regular at-home ketone tests are also a valuable tool for those following a keto meal plan. Knowing your ketone level can help you refine your dietary choices and provide motivation for reaching your health goals.

Brittany Cardwell, RDN, LD
Health Coach and Registered Dietitian Nutritionist @ PlateJoy

Brittany is a registered dietitian nutritionist with the Commission on Dietetic Registration and a licensed dietitian with the Ohio Board of Dietetics and the Tennessee Board of Dietitians. She is a graduate of Miami University (Ohio) with a Bachelor of Science in kinesiology and health, and holds a Certificate of Training in Adult Weight Management. An Ohio native, Brittany currently resides in Nashville with her husband, son and their fur baby. In her free-time she enjoys exploring new restaurants and coffee shops, attending barre classes and being outdoors.

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