Trace ketones in urine mean your body has started breaking down fat for energy instead of relying entirely on glucose. In most cases, this is a normal response to something routine like skipping a meal, exercising hard, or not drinking enough water. A trace reading falls at or below 0.6 mmol/L and is generally not a cause for concern on its own. However, for people with diabetes or during pregnancy, even trace amounts deserve a closer look because they can be an early signal of something more serious.
Why Your Body Produces Ketones
Your cells prefer to run on glucose, the sugar your body gets from carbohydrates. When glucose is scarce, your body pivots to its backup fuel source: stored fat. Fat cells release fatty acids into the bloodstream, which travel to the liver. There, the liver breaks those fatty acids down and converts them into molecules called ketone bodies.
This switch happens because of a metabolic bottleneck. When fat breakdown is happening faster than the liver can process the byproducts through its normal energy cycle, the excess gets funneled into ketone production. Hormones like glucagon and cortisol drive this process by signaling fat cells to release more fatty acids. At the same time, low insulin levels remove a chemical brake that normally limits how much fat the liver can import and burn. The result is a rising tide of ketones that spills into your blood and eventually your urine, where a dipstick test can pick it up.
Common Causes in Healthy People
The most frequent reason for trace ketones is simply not eating for a while. Fasting for more than 10 hours can trigger detectable ketones in urine, and the longer you go without food, the more likely they are to appear. One study found that healthy individuals developed measurable ketones after 3 to 6 days of fasting for over 10 hours per day. But you don’t need to fast for days. An overnight fast combined with a morning workout can be enough to produce a trace reading.
Other everyday triggers include:
- Low-carb or keto diets: Deliberately restricting carbohydrates forces your body into fat-burning mode, making trace (or higher) ketones expected.
- Intense exercise: Prolonged or vigorous activity can burn through your glucose reserves, prompting your liver to produce ketones.
- Dehydration: When you’re low on fluids, your urine becomes more concentrated. This can make a tiny amount of ketones appear more prominent on a dipstick, sometimes pushing a result from negative to trace.
- Illness with vomiting or diarrhea: Both deplete glucose stores and cause dehydration, a combination that reliably produces ketones.
If any of these apply to you and you’re otherwise healthy, trace ketones are typically harmless and will resolve once you eat, drink water, or recover from illness.
What the Dipstick Actually Measures
Your body makes three types of ketones. Standard urine dipsticks detect only one of them: acetoacetate. They have limited sensitivity to acetone and do not detect beta-hydroxybutyrate at all, even though that’s the most abundant ketone your body produces. This means a urine test gives you an incomplete picture.
There’s another important caveat. Research from Cornell University has shown that most trace reactions on dipsticks (around 5 mg/dL) are likely false positives caused by the natural color of the urine interfering with the test pad. Even some “small” readings at 15 mg/dL can be falsely elevated. So a single trace result, especially without symptoms, may not reflect real ketone production at all. If you’re concerned, retesting with a blood ketone meter gives a more accurate number.
Trace Ketones and Diabetes
For people with type 1 diabetes, and sometimes type 2, ketones carry a different weight. The concern is diabetic ketoacidosis (DKA), a dangerous condition where ketone levels climb so high they make the blood acidic. In DKA, blood ketone levels can reach 20 to 25 mmol/L, compared to the 0.6 mmol/L or less seen with a trace result. That’s a massive difference, but DKA doesn’t happen all at once. It builds.
Trace ketones can be the earliest warning sign that blood sugar is poorly controlled and the body is starting to rely on fat because insulin isn’t doing its job. The American Diabetes Association recommends that if you see trace or small ketones, you increase your fluid intake (water is best), take steps to bring blood sugar back into range, and retest in a few hours. If levels rise rather than fall, contact your doctor. The NHS advises that a urine ketone reading of 2+ or higher, or a blood level above 3 mmol/L, warrants emergency care.
Common situations that push a person with diabetes from trace ketones into dangerous territory include missed insulin doses, insulin pump malfunctions, acute illness, or infection. Knowing your baseline matters. If you have diabetes and see trace ketones with a blood sugar above 250 mg/dL, treat it as an early alert rather than something to dismiss.
Trace Ketones During Pregnancy
Ketones show up on prenatal urine tests for a variety of reasons, and a trace amount is generally considered okay. Morning sickness is one of the most common culprits: persistent vomiting drains glucose stores and causes dehydration, both of which promote ketone production. Skipping meals, eating a very low-carb diet, or over-exercising during pregnancy can do the same.
The bigger concern is unmanaged gestational diabetes, which is the most common cause of high ketone levels in pregnancy. If your blood glucose results have been unusually elevated, your provider may test for ketones to see whether your body is struggling to use glucose properly. Research on whether moderate ketone levels harm the fetus is mixed, but very high levels from uncontrolled diabetes are dangerous for both mother and baby and can signal DKA.
If trace ketones appear during pregnancy, the usual recommendation is to stay well-hydrated, eat regular meals with adequate carbohydrates, and address any underlying nausea. Your provider may recheck levels at a follow-up visit to confirm they’ve cleared.
Nutritional Ketosis vs. Ketoacidosis
If you’re following a ketogenic diet, seeing trace or even moderate ketones in your urine is the expected outcome. Nutritional ketosis typically produces blood ketone levels around 4 to 5 mmol/L, a range researchers have described as potentially beneficial for brain health. This is well below the 20 to 25 mmol/L seen in diabetic ketoacidosis or the 15 mmol/L associated with alcoholic ketoacidosis.
The key difference is insulin. In a healthy person, insulin acts as a governor, preventing ketone production from spiraling out of control. In type 1 diabetes, where insulin is absent or severely deficient, there’s no brake on the system. That’s why the same biological process (fat breakdown producing ketones) can be perfectly safe in one person and life-threatening in another.
What to Do About a Trace Reading
For most people without diabetes, a trace ketone result needs no medical intervention. Drink water, eat a meal that includes carbohydrates, and the ketones will clear as your body shifts back to burning glucose. If you’re on a low-carb diet and intentionally producing ketones, the reading simply confirms the diet is working as designed.
If you have diabetes, treat a trace reading as an early check-in. Hydrate, manage your blood sugar, and retest within a few hours. Rising levels mean something is off and your care plan may need adjusting. If you’re pregnant and seeing trace ketones alongside severe nausea or high blood sugar, mention it at your next appointment so your provider can assess whether further monitoring is needed.
One practical tip: because urine dipsticks can produce false positives at the trace level, a single isolated result with no symptoms and no risk factors is often meaningless. A blood ketone meter, which measures beta-hydroxybutyrate directly, provides a more reliable number if you want clarity.