Lab result explainedUrinalysisLast updated November 10, 2026

Ketones in urine: what trace, small, moderate and large ketones mean in diabetes, pregnancy and fasting

Ketones in urine · Urinalysis (dipstick) · reported in Reported as negative, trace, small, moderate or large, with approximate mg/dL of acetoacetate (5, 15, 40, 80, 160); some labs use 1+ to 4+ or mmol/L

Ketones in urine are acids (acetoacetate, beta-hydroxybutyrate and acetone) that the liver makes when the body is burning fat for fuel instead of glucose, and a urine dipstick detects them as a sign that this switch has happened. The normal result is negative. The two most common reasons for ketones in urine are not eating for a while (an overnight fast, skipped meals, vomiting, a low-carbohydrate diet) and, in people with diabetes, a shortage of insulin, which in its severe form is diabetic ketoacidosis (DKA), a medical emergency.

Results are graded as negative, trace (about 5 mg/dL), small (15), moderate (40) and large (80 to 160 mg/dL). Trace or small ketones in someone who has not eaten, has been vomiting, is exercising hard or is on a ketogenic diet are expected and usually harmless. Moderate or large ketones in anyone with diabetes, particularly with a high blood glucose, thirst, vomiting, abdominal pain or fast breathing, need urgent attention. In pregnancy, ketones most often reflect morning fasting or nausea, but moderate or large readings need a check.

The strip detects acetoacetate and, weakly, acetone, but not beta-hydroxybutyrate, which is the main ketone in DKA and in alcohol-related ketoacidosis. That means the urine test can under-read the most dangerous situations and can paradoxically rise during DKA treatment as beta-hydroxybutyrate is converted back to acetoacetate. For anyone with type 1 diabetes, a fingerstick blood ketone meter, which measures beta-hydroxybutyrate directly, is now the preferred test.

Ketones in urine at a glance

  • What it is: a dipstick test for acetoacetate (and acetone), by-products of fat burning that appear in urine when the body lacks glucose or insulin.
  • Normal: negative. Grades are trace (5 mg/dL), small (15), moderate (40), large (80–160 mg/dL); some labs report 1+ to 4+ or mmol/L (0.5, 1.5, 4, 8–16).
  • Trace to small ketones after fasting, vomiting, hard exercise or on a low-carb diet are expected and not harmful by themselves.
  • Moderate or large ketones with diabetes, especially with glucose above 240–250 mg/dL, nausea, vomiting, abdominal pain or fast breathing, suggest ketoacidosis: call your diabetes team or go to emergency care.
  • Blood ketones (beta-hydroxybutyrate): under 0.6 mmol/L normal; 0.6–1.5 check again in 2 hours; above 1.5 risk of DKA; 3.0 or more is DKA until proven otherwise.
  • Next step: eat and drink if the cause is fasting or vomiting and recheck; with diabetes, follow sick-day rules and check blood glucose and blood ketones; in pregnancy, mention it at your visit and seek care if you cannot keep food down.

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What Ketones in urine measures

When glucose is scarce, or insulin is too low for cells to use it, the liver breaks fatty acids down into ketone bodies: acetoacetate, which is converted to beta-hydroxybutyrate (the most abundant, usually 75 to 80 percent of the total in ketoacidosis) and spontaneously to acetone, which is breathed out and gives the fruity smell. Ketones are a normal fuel for the brain and muscles during fasting; they become dangerous only when produced faster than they can be used, which drives the blood acidic.

The dipstick pad contains sodium nitroprusside, which reacts with acetoacetate in an alkaline buffer to produce a purple color within 40 to 60 seconds; the deeper the color, the higher the concentration. The pad is about 5 to 10 times less sensitive to acetone and does not react with beta-hydroxybutyrate at all. Because urine collects over hours, the result reflects the average ketone level since you last emptied the bladder, not the level right now, and lags blood ketones by two to four hours in both directions.

Interference is mainly from drugs containing sulfhydryl groups, which give false positives: captopril, mesna, N-acetylcysteine and penicillamine. Levodopa, valproate metabolites, phenazopyridine and very dark, concentrated urine can also discolour the pad. False negatives occur when a sample sits for hours (acetoacetate breaks down to acetone, which evaporates) or when strips have absorbed moisture. In alcohol-related ketoacidosis and severe DKA the ratio of beta-hydroxybutyrate to acetoacetate can exceed 10 to 1, so the urine strip can read small when the blood ketone level is dangerously high.

Normal range for Ketones in urine

Reference ranges vary between labs and by age, sex and pregnancy. Use the range printed on your own report.

GroupTypical range (Reported as negative, trace, small, moderate or large, with approximate mg/dL of acetoacetate (5, 15, 40, 80, 160); some labs use 1+ to 4+ or mmol/L)Notes
NegativeNormalBelow about 5 mg/dL of acetoacetate. The expected result after a normal meal pattern.
TraceAbout 5 mg/dL (0.5 mmol/L)Common after an overnight fast, in early pregnancy, after exercise or on a low-carbohydrate diet. Not significant on its own.
Small (1+)About 15 mg/dL (1.5 mmol/L)Fasting, vomiting, dieting, prolonged exercise or mild insulin shortage. In diabetes, recheck glucose and ketones in 2 to 4 hours.
Moderate (2+)About 40 mg/dL (4 mmol/L)Significant ketosis. In diabetes with high glucose this is a warning of developing DKA; call your diabetes team. Without diabetes, usually prolonged fasting, severe vomiting or alcohol.
Large (3+ to 4+)80–160 mg/dL (8–16 mmol/L) or moreHeavy ketosis. In anyone with diabetes, or with vomiting, abdominal pain, fast breathing or drowsiness, treat as possible ketoacidosis and seek emergency care.
Blood beta-hydroxybutyrate (fingerstick meter)Under 0.6 mmol/L normal; 0.6–1.5 mild; 1.5–3.0 high risk; 3.0 or above DKA rangeThe preferred test in type 1 diabetes and for SGLT2-inhibitor users; it does not lag the way urine does.
Nutritional ketosis (ketogenic diet, by design)Blood 0.5–3.0 mmol/L; urine trace to moderate, falling over weeksExpected. Urine strips become unreliable after the first weeks because the kidney reabsorbs more ketones and the balance shifts to beta-hydroxybutyrate.
Pregnancy, first-morning sampleTrace to small is commonReflects overnight fasting and nausea. Moderate or large, or inability to keep fluids down, needs assessment the same day.

Positive ketones in urine (ketonuria)

Ketones in urine mean your body has been burning fat for fuel. In someone without diabetes, this is nearly always because of a shortage of carbohydrate: an overnight or longer fast, skipped meals, a low-carbohydrate or ketogenic diet, a stomach bug with vomiting, a fever in a child who is not eating, prolonged endurance exercise, breastfeeding, or heavy drinking without food. These states produce trace to moderate ketones, the blood does not usually become acidic, and the ketones clear within hours of eating and drinking. The exception is alcohol-related ketoacidosis, in which days of drinking and vomiting cause a genuine, sometimes severe, acidosis that the urine strip can under-read.

In someone with diabetes, ketones have a second, more serious meaning: not enough insulin. Without insulin, cells cannot take up glucose, so the liver makes ketones even though blood sugar is high. The combination of moderate or large urine ketones, a blood glucose above 240 to 250 mg/dL, and symptoms such as thirst, frequent urination, nausea, vomiting, abdominal pain, fruity breath, deep fast breathing or drowsiness is diabetic ketoacidosis until proven otherwise. DKA is diagnosed on blood tests (glucose above 250 mg/dL, pH below 7.3, bicarbonate 18 mEq/L or lower, blood ketones 3 mmol/L or higher) and treated in hospital with fluids and insulin. It is the presenting feature in about a third of new type 1 diagnoses in children in the US.

Two situations are easy to miss. People taking SGLT2 inhibitors (empagliflozin, dapagliflozin, canagliflozin and others) can develop euglycemic DKA with a blood glucose under 250 mg/dL, so ketones with nausea or malaise on these drugs are significant even when sugar looks fine. And in pregnancy, ketones are common after an overnight fast and with morning sickness, but pregnant women with type 1 diabetes develop DKA at lower glucose levels and more quickly than other adults, and any moderate or large ketones in pregnancy warrant a same-day call.

Common causes

  1. Fasting, skipped meals and very low-calorie diets

    After 12 to 18 hours without carbohydrate, liver glycogen is depleted and ketone production rises; trace to small ketones are routine in a first-morning sample from anyone who did not eat after dinner, and moderate ketones appear after 2 to 3 days of fasting.

  2. Low-carbohydrate and ketogenic diets

    Keeping carbohydrate under about 50 g a day deliberately produces nutritional ketosis (blood 0.5 to 3 mmol/L). Urine ketones are strongly positive in the first days and then fall as the kidney reabsorbs more and the liver shifts to beta-hydroxybutyrate, which the strip cannot see.

  3. Vomiting, gastroenteritis and febrile illness

    Not eating, losing fluid and the stress hormones of illness together push ketone production up. This is the usual cause of ketones in a child with a stomach bug or fever, and in adults with food poisoning or a migraine with vomiting.

  4. Diabetic ketoacidosis (type 1, and sometimes type 2 diabetes)

    Missed insulin, a failed pump, infection, heart attack or steroid use raise ketones because insulin is insufficient. Moderate to large ketones with glucose above 240 to 250 mg/dL, vomiting or abdominal pain is an emergency; so is any ketone reading with drowsiness or deep, fast breathing.

  5. SGLT2 inhibitors (euglycemic ketoacidosis)

    Empagliflozin, dapagliflozin, canagliflozin and ertugliflozin lower the glucose threshold for ketoacidosis; the FDA issued a warning in 2015. Ketones with nausea, malaise or abdominal pain on these drugs matter even when glucose is below 250 mg/dL, particularly around surgery, fasting or illness.

  6. Pregnancy, hyperemesis and gestational diabetes

    Pregnancy accelerates the switch to fat burning overnight, so trace to small ketones in a morning sample are common. Severe nausea (hyperemesis gravidarum) produces moderate to large ketones from starvation and dehydration; calorie-restricted diets for gestational diabetes can do the same.

  7. Alcohol binge with poor food intake

    Days of heavy drinking with little food, followed by vomiting, cause alcohol-related ketoacidosis, with abdominal pain, fast breathing and a normal or low glucose. Beta-hydroxybutyrate predominates, so the urine strip can read only small or moderate despite severe acidosis.

  8. Prolonged or intense exercise

    Marathons, long cycling events and multi-hour workouts deplete glycogen and raise ketones to trace or small for several hours afterwards, more so if the exercise was done fasted.

  9. Breastfeeding, hyperthyroidism and acute illness

    Lactation raises energy needs and ketone production, particularly with low carbohydrate intake. Thyrotoxicosis, severe infection, major surgery and trauma increase fat breakdown through stress hormones.

  10. Drug and sample interference (false positives)

    Captopril, mesna, N-acetylcysteine, penicillamine, levodopa, valproate and phenazopyridine can turn the pad purple without ketones. Very concentrated, dark urine can also give a faint false positive. Re-test on a fresh sample, or use a blood ketone meter.

Symptoms that can go with it

  • None with trace or small ketones from fasting, dieting or exercise
  • Fruity or sweet-smelling breath, metallic taste
  • Thirst, dry mouth, passing a lot of urine (with high glucose in diabetes)
  • Nausea, vomiting, loss of appetite, abdominal pain
  • Fatigue, weakness, headache, difficulty concentrating (common in the first week of a ketogenic diet)
  • Deep, rapid breathing (Kussmaul breathing), drowsiness or confusion: signs of ketoacidosis, an emergency
  • In pregnancy: inability to keep food or fluids down, dizziness, reduced urination
  • In children: lethargy, refusal to drink, dry lips and few wet nappies with a stomach bug

Read it alongside

  • Glucose in urine and blood glucose — ketones with glucose above 240 to 250 mg/dL (or glycosuria 2+ or more) in diabetes suggests DKA; ketones with normal or low glucose suggest fasting, vomiting, alcohol or SGLT2-inhibitor ketoacidosis.
  • Blood beta-hydroxybutyrate — the direct measurement; 3 mmol/L or more with symptoms is DKA, and it is the test that catches euglycemic and alcohol-related ketoacidosis the urine strip misses.
  • CO2 (bicarbonate) and anion gap — a bicarbonate of 18 mEq/L or lower with a raised anion gap confirms acidosis rather than simple ketosis.
  • Urine specific gravity — very concentrated urine (above 1.030) with ketones points to dehydration from vomiting, fasting or osmotic diuresis.
  • Sodium and potassium — DKA shifts both; potassium is often high at presentation and falls fast with insulin, which is why it is checked repeatedly in hospital.
  • A1C — ketones with a high A1C suggest sustained insulin shortage; ketones with a normal A1C point to fasting, illness or diet rather than diabetes.
  • Lactic acid — distinguishes lactic acidosis (sepsis, metformin, shock) from ketoacidosis when the anion gap is raised.
  • Lipase and liver enzymes — abdominal pain with ketones is sometimes pancreatitis or hepatitis rather than, or as well as, DKA.

What usually happens next

  1. If you do not have diabetes and the ketones are trace to small after fasting, vomiting, exercise or a low-carbohydrate diet, eat a meal containing carbohydrate, drink fluids and recheck in a few hours; the result should be negative within a day.
  2. If you have diabetes and ketones are trace or small with glucose under 240 mg/dL and you feel well, drink water, take your usual insulin and recheck glucose and ketones in 2 to 4 hours; follow the sick-day rules your diabetes team gave you.
  3. If you have diabetes and ketones are moderate or large, or glucose is above 240 to 250 mg/dL with any ketones, or you are vomiting, call your diabetes team now or go to emergency care; do not exercise, which raises ketones further.
  4. If you take an SGLT2 inhibitor and have nausea, abdominal pain or malaise with any ketones, seek care the same day even if glucose is normal; these drugs are usually paused around surgery, fasting and acute illness.
  5. In pregnancy, mention ketones at your visit; if you cannot keep fluids down, have moderate or large ketones, or have diabetes with any ketones, contact your maternity unit the same day.
  6. Ask: what was my glucose at the same time, should I have a blood ketone meter, what are my sick-day rules, and could any of my medicines interfere with the strip?

Diet, lifestyle and natural levers with evidence

What can move Ketones in urine once the cause is known. Nothing here replaces finding the cause.

Eat regular meals with carbohydrate (if ketones are unintended)

Strong evidence

Fasting ketosis reverses within hours of eating. Insulin released after a meal containing 50 g or more of carbohydrate switches off hepatic ketone production, and urine ketones from an overnight fast are typically negative by the second void after breakfast. In people with gestational diabetes, spreading intake over three meals and two to three snacks, including a bedtime snack, is the standard advice to prevent morning ketonuria, and diets below about 1,600 to 1,800 kcal a day are avoided for this reason.

Fluids and oral rehydration during vomiting illnesses

Moderate evidence

Ketones in gastroenteritis come from not eating and from dehydration. Small, frequent sips of an oral rehydration solution, which contains glucose, both rehydrate and suppress ketone production, and in children with gastroenteritis trials show that oral rehydration with glucose-containing solution clears ketosis as effectively as intravenous fluids in those who can keep it down. Plain water alone does not supply the carbohydrate needed to stop ketogenesis.

Not a substitute for emergency care in diabetic ketoacidosis, or in anyone who cannot keep fluids down, is drowsy or is breathing fast.

Avoid heavy drinking on an empty stomach

Moderate evidence

Alcohol-related ketoacidosis follows binge drinking combined with little food and vomiting; case series show it resolves within 12 to 24 hours of glucose-containing fluids and thiamine, and it does not develop when drinking is accompanied by regular meals. Keeping intake within recommended limits and never drinking in place of eating removes the risk almost entirely.

Anyone with abdominal pain, fast breathing or confusion after a binge needs emergency assessment; this cannot be managed at home.

Know what a ketogenic diet does to the test

Strong evidence

Keeping carbohydrate below about 50 g a day reliably produces nutritional ketosis, with blood beta-hydroxybutyrate of 0.5 to 3 mmol/L and positive urine strips, and this is the intended effect rather than a problem. Trials of ketogenic diets in type 2 diabetes and epilepsy report blood ketones in this range without acidosis in people with normal insulin production. Urine strips read lower after the first few weeks even when blood ketones are stable, so a blood meter is a better guide if you are tracking ketosis.

People with type 1 diabetes, those on SGLT2 inhibitors, and pregnant or breastfeeding women should not start a ketogenic diet without medical supervision; ketoacidosis has been reported in all three groups. Tell any clinician ordering a urinalysis that you are on the diet.

Fuel before and after long exercise

Moderate evidence

Ketones after endurance exercise reflect glycogen depletion. Studies of marathon runners and cyclists show post-exercise blood ketones of 0.5 to 2 mmol/L when exercise is done fasted or after low-carbohydrate meals, versus near-normal levels when 30 to 60 g of carbohydrate an hour is taken during prolonged sessions. Eating within an hour or two afterwards brings urine ketones back to negative.

People with diabetes should not exercise with moderate or large ketones, since exercise raises them further and can precipitate DKA.

When to see a clinician promptly

  • Moderate or large ketones in anyone with diabetes, or any ketones with blood glucose above 240 to 250 mg/dL, nausea, vomiting, abdominal pain, fruity breath, deep fast breathing, drowsiness or confusion: possible diabetic ketoacidosis, go to emergency care now.
  • Ketones with nausea, malaise or abdominal pain while taking an SGLT2 inhibitor, even if glucose is normal: possible euglycemic ketoacidosis, same-day assessment.
  • Ketones in pregnancy with inability to keep fluids down, dizziness, reduced urination, or any ketones if you have type 1 diabetes: contact your maternity unit the same day.
  • A child with ketones who is lethargic, refusing fluids, breathing fast, has few wet nappies or whose vomiting has lasted more than 24 hours.
  • Ketones with fast breathing, abdominal pain or confusion after heavy drinking: possible alcohol-related ketoacidosis, an emergency.
  • Persistent moderate ketones with weight loss, thirst and frequent urination in someone not known to have diabetes: these are the classic symptoms of new type 1 diabetes and need same-day blood tests.

Frequently asked questions

What do ketones in urine mean?

They mean your body is burning fat for fuel because it is short of glucose or, in diabetes, short of insulin. Trace to small ketones after an overnight fast, vomiting, hard exercise or on a low-carbohydrate diet are expected and harmless on their own. Moderate or large ketones in someone with diabetes, with high blood sugar, vomiting or abdominal pain, signal diabetic ketoacidosis and need urgent care.

Are trace ketones in urine bad?

Usually not. Trace (about 5 mg/dL) is the amount produced by skipping a meal, an overnight fast, a long workout, a stomach bug or the first days of a low-carb diet, and it clears within hours of eating. In diabetes, trace ketones with normal glucose are a prompt to drink fluids and recheck in a few hours rather than an emergency; they become important if glucose is high, if they rise to moderate, or if you feel unwell.

What causes ketones in urine if you are not diabetic?

Not eating for 12 hours or more, dieting, low-carbohydrate eating, vomiting or diarrhea, fever (especially in children), prolonged exercise, pregnancy, breastfeeding, heavy alcohol use without food, and an overactive thyroid. A few drugs, including captopril, N-acetylcysteine, mesna, levodopa and valproate, can give a false positive on the strip. If ketones are moderate or large with thirst, weight loss and frequent urination, undiagnosed diabetes needs to be excluded with a blood test.

Are ketones in urine during pregnancy dangerous?

Trace to small ketones in a morning sample are common in pregnancy because pregnancy speeds the overnight switch to fat burning, and with nausea and vomiting. They are not thought to harm the baby at that level. Moderate or large ketones usually mean you are not keeping enough food or fluid down (hyperemesis gravidarum) or, if you have diabetes, that insulin is insufficient; both need same-day assessment, because DKA in pregnancy can develop quickly and at lower glucose levels than usual.

What ketone level is dangerous in diabetes?

On urine strips, moderate (40 mg/dL) or large (80 mg/dL or more) is the danger zone, particularly with glucose above 240 to 250 mg/dL or any vomiting. On a blood ketone meter, under 0.6 mmol/L is normal, 0.6 to 1.5 means recheck in 2 hours and take extra fluids and insulin as your sick-day plan directs, above 1.5 means contact your diabetes team, and 3.0 or more means go to emergency care. Symptoms such as vomiting, abdominal pain, deep breathing or drowsiness override the number.

Why does the urine ketone strip miss DKA or read higher during treatment?

The strip detects acetoacetate but not beta-hydroxybutyrate, which makes up most of the ketones in DKA and in alcohol-related ketoacidosis. Early on, the strip can read small while blood ketones are high. As treatment with insulin works, beta-hydroxybutyrate is converted back to acetoacetate, so the urine reading can rise even as the patient improves. This is why hospitals and people with type 1 diabetes now use blood beta-hydroxybutyrate meters.

Will a keto diet show ketones in urine?

Yes, that is the point of the diet. In the first one to two weeks urine strips typically read small to moderate. After that they often fade to trace or negative even though blood ketones stay at 0.5 to 3 mmol/L, because the kidney reabsorbs more ketones and the balance shifts to beta-hydroxybutyrate. Blood meters are more reliable for tracking. Mention the diet if you have a urinalysis so the result is not mistaken for illness.

How do I get rid of ketones in my urine?

If the cause is fasting, dieting, exercise or vomiting, eat a meal with carbohydrate and drink fluids; ketones usually clear within 12 to 24 hours. If you have diabetes, follow your sick-day rules: fluids, the extra insulin your plan specifies, and glucose and ketone checks every 2 to 4 hours, with a call to your team if ketones are not falling. Do not exercise with moderate or large ketones. If you are vomiting, drowsy or breathing fast, this cannot be managed at home.

References

  1. Ketones in urine. MedlinePlus, US National Library of Medicine (2023)View source
  2. Diabetic ketoacidosis. Mayo Clinic (2022)View source
  3. Diabetic ketoacidosis (DKA). Merck Manual Professional Version (2024)
  4. Kitabchi AE, Umpierrez GE, Miles JM, Fisher JN. Hyperglycemic crises in adult patients with diabetes. Diabetes Care (2009)
  5. Umpierrez GE, Davis GM, ElSayed NA, et al.. Hyperglycaemic crises in adults with diabetes: a consensus report (ADA, EASD, JBDS, AACE, DTS). Diabetes Care (2024)
  6. Laffel L. Ketone bodies: a review of physiology, pathophysiology and application of monitoring to diabetes. Diabetes/Metabolism Research and Reviews (1999)
  7. Nausea and vomiting of pregnancy: ACOG Practice Bulletin No. 189. Obstetrics & Gynecology, American College of Obstetricians and Gynecologists (2018)
  8. Gestational diabetes mellitus: ACOG Practice Bulletin No. 190. Obstetrics & Gynecology, American College of Obstetricians and Gynecologists (2018)
  9. Rizzo T, Metzger BE, Burns WJ, Burns K. Correlations between antepartum maternal metabolism and child intelligence. New England Journal of Medicine (1991)
  10. Simerville JA, Maxted WC, Pahira JJ. Urinalysis: a comprehensive review. American Family Physician (2005)
  11. McGuire LC, Cruickshank AM, Munro PT. Alcoholic ketoacidosis. Emergency Medicine Journal (2006)

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This page is educational and is not medical advice or a diagnosis. Lab results have to be interpreted together with your history, symptoms and other results by a clinician who knows you. Do not start or stop a supplement to change a lab value before the cause is known.