Ketones in your urine mean your body is burning fat for fuel instead of its preferred energy source, glucose. This happens when your cells can’t access enough glucose, whether from fasting, a low-carb diet, intense exercise, illness, or a problem with insulin. A small amount of ketones can be completely normal in certain situations, but moderate to high levels can signal a serious medical emergency, especially if you have diabetes.
Why Your Body Makes Ketones
Your cells normally run on glucose, the sugar your body breaks down from carbohydrates. When glucose is scarce or your body can’t use it properly, your liver switches to a backup system: it pulls fatty acids out of stored fat and converts them into molecules called ketone bodies. These ketones travel through your bloodstream and serve as an alternative fuel source for your brain, heart, and muscles.
This process ramps up whenever counter-regulatory hormones like glucagon rise. Glucagon signals your fat cells to release stored fat into the bloodstream, and your liver then oxidizes those fatty acids into ketones. In small amounts, this is a perfectly normal survival mechanism. Your body does it overnight while you sleep, during a long stretch without food, or after a hard workout. The ketones that aren’t used for energy get filtered out by your kidneys and end up in your urine.
Common Causes Beyond Diabetes
Diabetes is the most common cause of dangerously high ketones, but plenty of non-diabetic situations produce them too:
- Skipping meals or fasting. Going without food for an extended period depletes your glucose stores, pushing your liver into fat-burning mode.
- Low-carb or ketogenic diets. Deliberately cutting carbohydrates triggers the same shift. Trace to small ketone levels on a urine strip are expected and, for people following these diets intentionally, considered a sign the diet is “working.”
- Dehydration. Less water in your system concentrates the ketones already present, making levels appear higher on a test.
- Prolonged vomiting or diarrhea. Both deplete fluids and prevent you from keeping food down, so your body turns to fat for energy.
- Intense or prolonged exercise. Hard training burns through your glycogen reserves quickly, especially if you haven’t eaten enough carbohydrates beforehand.
- Illness or infection. When you’re sick, stress hormones spike and appetite drops, both of which promote ketone production.
In most of these cases, ketone levels return to normal once you eat, rehydrate, or recover from the illness. A trace or small reading on a urine strip in these situations is not typically dangerous.
Ketones in Urine During Pregnancy
Pregnant women are sometimes surprised to see ketones flagged on routine urine tests. Morning sickness is a frequent culprit: repeated vomiting prevents you from keeping carbohydrates down, so your body dips into fat stores. Skipping meals, dehydration, or following a restrictive diet during pregnancy can have the same effect.
For pregnant women with diabetes (type 1, type 2, or gestational), ketones carry extra concern. When blood sugar runs too high and ketones build up, those ketones can cross the placenta and potentially affect the baby. Managing blood sugar closely and eating regular meals with adequate carbohydrates helps keep ketone production in check during pregnancy.
When Ketones Signal a Diabetes Emergency
For people with diabetes, ketones in urine can be an early warning sign of diabetic ketoacidosis, or DKA. This happens most often in type 1 diabetes, where the body produces little or no insulin. Without insulin, glucose can’t enter cells at all, so the liver floods the bloodstream with ketones. At the same time, the body can’t clear ketones efficiently because insulin is needed for that process too. Ketone levels spiral upward, making the blood dangerously acidic.
DKA can also develop in type 2 diabetes during severe illness, surgery, or missed medications. A urine ketone reading of 2+ or higher, combined with elevated blood sugar, raises clinical suspicion for DKA. Warning signs that need immediate emergency care include:
- Excessive thirst and frequent urination
- Nausea, vomiting, or abdominal pain
- Fruity-scented breath
- Shortness of breath
- Confusion or difficulty staying alert
- Weakness or extreme fatigue
Untreated DKA can be fatal. If you have diabetes and notice moderate to large ketones on a urine test alongside any of these symptoms, treat it as an emergency.
A Medication That Changes the Picture
A class of diabetes medications called SGLT2 inhibitors (common brand names include Jardiance, Farxiga, and Invokana) adds a complication worth knowing about. These drugs work by forcing your kidneys to excrete excess glucose into your urine. That’s helpful for blood sugar control, but it also raises glucagon levels and promotes ketone production.
The tricky part: these medications can cause DKA even when your blood sugar reads normal. This is called euglycemic DKA, and it accounts for roughly two-thirds of the DKA cases reported to the FDA in connection with SGLT2 inhibitors. An FDA analysis found a sevenfold increased risk of DKA with these medications. If you take an SGLT2 inhibitor and start feeling nauseated, unusually tired, or generally unwell, don’t assume you’re fine just because your blood sugar looks good. Testing your urine for ketones can catch the problem early.
How Urine Ketone Tests Work
Urine ketone tests use a simple dipstick: you either hold the strip in your urine stream or dip it into a collected sample, then compare the color change to a chart on the bottle. The strip reacts with a chemical called nitroprusside, which detects two of the three types of ketone bodies (acetoacetate and acetone). It does not detect beta-hydroxybutyrate, which is actually the most abundant ketone in your blood during ketoacidosis. This means a urine dipstick can underestimate how many ketones your body is actually producing.
Results typically read as negative, trace, small, moderate, or large. One important limitation: urine tests reflect what your ketone levels were over the past few hours, not what they are right now. Blood ketone meters, which directly measure beta-hydroxybutyrate, give a more accurate real-time picture. If you have diabetes and are monitoring for DKA risk, a blood ketone meter is the more reliable tool.
What to Do About Your Results
A trace or small reading without diabetes or other symptoms usually doesn’t require any action beyond eating a balanced meal and drinking water. If you’ve been fasting, exercising hard, or following a keto diet, trace ketones are expected.
Moderate ketones deserve attention. If you have diabetes, check your blood sugar, drink water, and contact your healthcare team. Avoid exercising, which can raise ketone levels further. If you don’t have diabetes but have been vomiting repeatedly or can’t keep fluids down, moderate ketones suggest you need help rehydrating.
Large ketones with symptoms like nausea, abdominal pain, or fruity breath require emergency care regardless of what your blood sugar says. This is especially true if you have type 1 diabetes or take an SGLT2 inhibitor. Speed matters: the earlier DKA is caught, the simpler and safer the treatment.