Ketones in Urine: When and Why to Test for Them and What They Mean

Your body typically uses glucose, or sugar, as its main source of energy. When cells don’t get the glucose they need, the body begins to use fat instead. Burning fat produces ketones, a type of acid that ends up in your blood and urine that can make you very sick.

Doctors regularly test for ketones in the urine of people with type 1 and type 2 diabetes, though ketones are more common among people with type 1 diabetes. If you have diabetes and have higher levels of ketones in your urine than normal, your body is not getting the insulin it needs to transfer sugar from your blood to your cells to be used as energy. (1) This can result in hyperglycemia, or high blood sugar, which can lead to serious complications such as heart disease, stroke, vision problems, and nerve damage if not properly managed.

What Causes High Levels of Ketones in Urine?

For people diagnosed with diabetes, high levels of ketones in urine can be caused by illness, missing an insulin shot, an ineffective insulin pump, or not getting enough insulin. (2) It can also occur when a person has missed a meal or has not eaten enough. (3)

In addition to diabetes, you may also be at risk for ketones in urine if you have or experience the following: (4)

• Pregnancy
• Eating disorder
• Strenuous exercise
• Chronic vomiting or diarrhea
• Eating a low-carbohydrate diet
• Pneumonia
• Alcohol abuse
• Infection
• Heart attack
• Stroke
• Fasting
• High fever
• Sepsis
• Burns
• Hyperthyroidism
• Nursing a baby without proper nutrition

A test to detect ketones in urine can be administered at home or in a lab. Sometimes patients are asked not to eat or drink for a specified amount of time before they take the test.

When testing in a lab, patients are advised to wash their hands and then clean their genital area via a sterile cleansing pad. Patients must then collect 1 to 2 ounces of urine into a container, and give the sample to the appropriate healthcare provider. (1)

Patients can also test for ketones in urine at home by doing a spot test, which uses urine test strips. You can capture the urine in a clean container and dip the test strip into the container, or you can urinate directly onto the test strip. Follow the instructions to see how long after testing you should read the color of the strip. Then compare the strip color with the color chart on the bottle. (5)

If you are testing for ketones in babies or toddlers who wear diapers, clean cotton wool can also be used to capture urine. (5)

When testing your urine for ketones, it’s important to make sure that the test strips have not expired.

You do not need a prescription to obtain a ketone test kit from your local pharmacy. Talk to your doctor about which test kit could work best for you and provide the most relevant information.

Results of the ketones urine test can be measured by a numerical score or categorized qualitatively as a small, moderate, or large amount of ketones. What’s considered a normal amount of ketones in urine will vary by age, gender, health history, and other factors, so be sure to talk to your doctor about your exercise and diet habits, as well as other factors that might affect your typical level. (1)

When Should I Have a Test for Ketones in Urine?

If you have diabetes or another condition that puts you at risk for high levels of ketones, a healthcare provider will generally advise you to test for ketones every 4 to 6 hours when you experience any of the following: (3)

• Blood glucose level above 240 milligrams per deciliter (mg/dl)
• Vomiting or feelings of nausea
• Abdominal pain
• Other illnesses, such as cold or flu
• Constant fatigue
• Dry mouth or constant thirst
• Flushed skin
• Fruity-smelling breath
• Confusion

If your child has diabetes and becomes sick, he or she will need extra attention and consultation with doctors. Notify the child’s diabetes team immediately if your child has a fever, vomiting, or diarrhea. Also, contact a doctor if your child’s urine tests positive for ketones. (5)

What Does an Abnormal Result for a Ketones in Urine Test Mean?

Abnormal results typically break down as follows: (4)

• Small: 20 mg/dl
• Moderate: 30 to 40 mg/dl
• Large: >80 mg/d

If you test for ketones in your urine and the results indicate a small amount, consult with your doctor and continue retesting every few hours. (3)

If test results show moderate or large amounts of ketones in urine, contact your healthcare provider immediately. It’s also important not to exercise when ketone levels are high or when your blood sugar is high, as this can worsen the effects. (3)

If test results show high levels of ketones in your urine, your doctor may check the amount of ketones in your blood and also conduct the following urine tests: (7)

• Blood glucose
• Protein
• pH (or acid level)

High levels of ketones detected in your urine are a potential indicator of diabetic ketoacidosis (DKA), a severe complication of diabetes. Diabetic ketoacidosis is often the first sign that a person has diabetes before they are diagnosed. (2)

If you become ill and have diabetes, your blood sugar and ketone levels can rise and cause ketoacidosis. Consult with your healthcare provider about how to monitor your ketone and blood glucose levels and how to prevent ketoacidosis when you’re sick. (2)

Additional symptoms of ketoacidosis can include: (1)

• Trouble breathing
• Nausea
• Vomiting
• Unusual thirst
• Fruity-smelling breath
• Flushed skin
• Abdominal pain
• Confusion
• Sleepiness
• Unconsciousness

It’s important to seek help for DKA immediately, as it can lead to a diabetic coma or even death. (3)

1. Diabetes Research Institute Foundation
2. American Diabetes Association
3. National Institute of Diabetes and Digestive and Kidney Diseases