Having ketones in your urine means your body is burning fat for fuel instead of its preferred energy source, glucose. In many cases this is completely harmless and temporary, caused by something as routine as skipping a meal or getting a long night’s sleep. But in certain situations, especially for people with diabetes, elevated ketones can signal a dangerous metabolic emergency that needs immediate attention.
Why Your Body Produces Ketones
Your cells normally run on glucose, which comes from the carbohydrates you eat. When glucose is unavailable or your body can’t use it properly, your liver switches to a backup system: it breaks down stored fat into fatty acids, then converts those fatty acids into molecules called ketone bodies. These ketones travel through your bloodstream and serve as an alternative energy source for your brain, heart, and muscles.
Small amounts of ketones are a normal part of metabolism. Your body produces them every night while you sleep, since you’re going hours without eating. The ketones get filtered by your kidneys and show up in your urine. At trace levels, this is routine biology, not a medical problem.
The concern starts when ketone production outpaces what your body can use. Ketones are acidic, and when they accumulate in large quantities, they lower your blood’s pH. That shift toward acidity is what makes high ketone levels dangerous.
Common Causes in People Without Diabetes
Several everyday situations can push your body into fat-burning mode and produce detectable ketones in urine:
- Fasting or skipping meals: Going without food for an extended period depletes your glucose stores and triggers fat breakdown.
- Low-carb or keto diets: A ketogenic diet is specifically designed to keep carbohydrate intake very low, forcing your body to rely on fat for energy. Ketones in urine are an expected result.
- Prolonged intense exercise: When you burn through all your stored glucose (glycogen) during a hard workout, your body shifts to fat as fuel.
- Prolonged vomiting or diarrhea: Extended illness can deplete your glucose supply and leave your body relying on fat reserves.
- Eating disorders or starvation: Severe calorie restriction limits available glucose, leading to sustained ketone production.
- Alcohol use disorder: Heavy alcohol consumption can trigger a condition called alcoholic ketoacidosis, where the combination of poor nutrition and alcohol’s metabolic effects drives ketone levels up.
In these scenarios, ketones typically return to normal once you eat carbohydrates again or the underlying trigger resolves. Trace to small amounts on a urine test are usually not a cause for concern in otherwise healthy people.
Why Ketones Are Especially Serious With Diabetes
For people with diabetes, ketones in urine carry a different meaning. The most dangerous possibility is diabetic ketoacidosis (DKA), a life-threatening emergency that develops when the body doesn’t have enough insulin to move glucose into cells. Without insulin, cells starve despite high blood sugar levels, and the liver ramps up ketone production dramatically.
DKA is diagnosed when three things happen together: blood glucose at or above 200 mg/dL, high ketone levels (a urine strip reading of 2+ or greater, or blood ketones at or above 3 mmol/L), and the blood becoming too acidic. DKA is most common in type 1 diabetes but can occur in type 2 as well, particularly during illness, infection, or missed insulin doses.
Warning signs that ketones have reached dangerous levels include nausea and vomiting, abdominal pain, breath that smells fruity or sweet, rapid deep breathing, confusion or difficulty concentrating, and extreme thirst with frequent urination. If you have diabetes and notice these symptoms alongside positive ketone tests, this is an emergency.
A Medication-Related Complication to Know About
A class of diabetes medications called SGLT2 inhibitors (prescribed under names like empagliflozin, dapagliflozin, and canagliflozin) can cause a tricky variant called euglycemic ketoacidosis. In this situation, your blood sugar stays below 200 mg/dL, so neither you nor your doctor may immediately suspect DKA, but your blood is still dangerously acidic from ketone buildup. These medications work by making your kidneys flush out extra glucose, which can, through a chain of hormonal shifts, ramp up ketone production. If you take one of these medications and feel unusually unwell, testing for ketones is important even if your blood sugar looks fine.
Ketones During Pregnancy
Ketones in urine during pregnancy can show up for several reasons: dehydration, severe morning sickness causing prolonged vomiting, or not getting adequate nutrition. They can also be a sign of gestational diabetes.
Research is mixed on whether mildly elevated ketones pose a risk to the fetus. Ketone levels below 0.5 mmol/L are generally considered within a normal range during pregnancy. However, very high levels, typically from unmanaged diabetes, are dangerous for both the pregnant person and the developing baby and can indicate DKA. If you’re pregnant and your provider finds ketones on a routine urine test, it usually prompts further evaluation to rule out gestational diabetes and ensure you’re staying hydrated and well-nourished.
How Ketone Testing Works
The most common way to check for ketones is a urine dipstick test, either at a doctor’s office or with an at-home kit you can buy at a pharmacy. You dip the strip into a urine sample and compare the color change to a chart on the packaging. Results typically range from negative to trace, small, moderate, and large.
One important limitation: urine strips reflect your ketone levels from several hours earlier, not in real time. They can also give inaccurate readings if you’re dehydrated. Blood ketone meters, which use a finger-prick sample similar to a glucose monitor, give a more current and precise measurement. For people with diabetes who need to monitor ketones closely, blood meters are the more reliable option.
People following a keto diet often use urine strips to confirm they’ve entered ketosis. This works reasonably well in the first few weeks, but over time, your body becomes more efficient at using ketones, and fewer spill into urine, which can make the strips appear falsely low even though you’re still in ketosis.
What Different Levels Mean for You
Trace or small ketone readings in a healthy person who has been fasting, exercising hard, or eating low-carb are usually nothing to worry about. Your body is doing exactly what it’s designed to do when glucose runs low.
Moderate to large readings deserve more attention. If you don’t have diabetes, moderate ketones alongside vomiting, diarrhea, or an inability to eat may mean you’re becoming significantly dehydrated and need medical evaluation. If you do have diabetes, moderate or large ketones, especially paired with blood sugar above 200 mg/dL, warrant contacting your healthcare provider promptly or seeking emergency care if you feel unwell.
Context matters more than any single number. A moderate reading in someone who just finished a 24-hour fast means something entirely different from the same reading in a person with type 1 diabetes who missed their insulin. The ketone level itself is one piece of the puzzle; your symptoms, medical history, and blood sugar levels together determine whether it’s routine or urgent.