Ketones in Urine: What Does It Mean and When Is It Serious?

Ketones in urine mean your body has been burning fat for energy because it could not get or use enough glucose. Small or trace amounts can be normal, for example after an overnight fast or on a very low-carbohydrate diet. Moderate or large amounts, or any ketones with diabetes and feeling unwell, need prompt medical advice because they can signal diabetic ketoacidosis.

This guide is for adults reading a home strip or a urinalysis report. It explains common reasons and warning signs. It cannot tell you why ketones are present in your case or how urgent your situation is.

Diabetic ketoacidosis (DKA) is a medical emergency. It is most common in type 1 diabetes, but it can happen in type 2 diabetes, and it is sometimes the first sign of diabetes in someone who has not been diagnosed. Call your local emergency number or go to an emergency department if ketones come with any of these:

• Vomiting that stops you keeping food or fluids down.
• Fast, deep breathing or trouble breathing.
• Fruity-smelling breath.
• Confusion, unusual sleepiness or extreme tiredness.
• Stomach pain with nausea, strong thirst and passing urine often.
• Symptoms of DKA when you do not know your ketone level, or when you have not been diagnosed with diabetes.

If you have diabetes, follow the sick-day plan from your own diabetes team first, because normal and safe levels can differ between people. As general public guidance, the NHS advises calling the emergency number or going to A&E if urine ketones are over 2+ or blood ketones are over 3 mmol/L. It advises urgent contact with your diabetes team for blood ketones from 1.6 to 3 mmol/L, even if you feel well.

The CDC advises people with diabetes to test urine for ketones when they are sick or when blood sugar is 250 mg/dL or higher, and to seek emergency care if blood sugar stays at 300 mg/dL or higher. Do not stop or skip insulin because you are not eating unless your care team has told you to. Do not drive yourself to hospital if you feel unwell.

A class of diabetes medicines called SGLT2 inhibitors can rarely cause DKA in which blood glucose is only moderately raised or near normal. The UK medicines regulator advises testing for ketones when someone taking one has DKA symptoms, even if glucose readings do not look high.

Yes. When carbohydrate intake is low, the body breaks down fat and makes ketones. Cleveland Clinic notes that trace ketones after an overnight or longer fast are normal, and that people following a strict ketogenic diet typically show ketones on a urine test.

Prolonged, intense exercise can have a similar effect by using up stored glucose. MedlinePlus advises talking with a clinician before starting a keto diet, because it may not suit people with some health conditions, including diabetes. A diet-related result is not a reason to ignore symptoms; feeling very unwell with ketones still needs assessment.

Prolonged vomiting or diarrhoea can leave the body short of glucose, so it burns fat and makes ketones. Other listed causes include eating disorders or starvation, some digestive diseases, and long-term heavy alcohol use, which can cause alcohol-related ketoacidosis.

In people with diabetes, illness can also push blood sugar up and make DKA more likely. That is why diabetes sick-day rules usually include more frequent glucose and ketone checks. Ask your team for written sick-day rules if you do not already have them.

If you do not have diabetes and keep vomiting, signs of dehydration matter as much as the strip. Little or no urine, dizziness, confusion or being unable to keep fluids down are reasons to get medical help the same day, whatever the ketone reading shows.

Ketones can appear in urine during pregnancy. Cleveland Clinic names gestational diabetes as a common reason, and the other causes above, such as vomiting or not eating, can also apply. Your midwife or doctor will interpret the result alongside your glucose tests and symptoms.

Severe pregnancy sickness (hyperemesis gravidarum) can cause dehydration, with thirst, dizziness, little urine and dark urine. The NHS advises telling your midwife or doctor, or contacting the hospital, as soon as possible if you cannot keep food down.

Home urine strips are sold without a prescription. Results are usually shown as negative, trace, small, moderate or large, or as a plus-sign scale. Follow the kit instructions exactly, including timing and storage, because errors can change the reading.

A urine strip reflects ketones made over the past few hours, not the level at that moment. Many people with diabetes are advised to use blood ketone testing instead. Cleveland Clinic advises people with diabetes to contact their provider for any level above trace, and describes moderate or large amounts as a serious risk of ketoacidosis. In someone without diabetes, it describes moderate or large amounts as abnormal.

Bring the strip result or report, the time of the test, what you had eaten, any vomiting or illness, and your glucose readings if you check them.

• Is this amount of ketones expected with my diet, fasting or illness, or does it need more tests?
• Should I check blood glucose or blood ketones, and how often?
• What ketone level or symptom means I should call you, and what means I should go to the emergency department?
• Could any of my medicines affect my ketone risk?
• If I am pregnant, how does this result fit with my glucose tests and how much I can eat and drink?
• What should my sick-day plan be?

On SameCase, patients and verified doctors share de-identified cases. Reading how others described the timing of a ketone result, their diet, illness and the questions they asked can help you organise your own notes before an appointment.

We cannot diagnose you, and another person's case cannot tell you what your result means. If you have symptoms of DKA, seek emergency care first rather than looking for similar cases.