How to Check Ketones: Urine Strips vs a Blood Ketone Meter
Ketones are the early warning for diabetic ketoacidosis (DKA), often before you feel seriously ill. There are two ways to check them at home, and they do not measure the same thing. Here is how each works, what the numbers mean, and when a result means getting help.
This article is general education, not medical advice. Your own sick-day plan from your care team comes first. If you have high ketones, vomiting, confusion or trouble breathing, get emergency help.
Why Ketones Matter
Without enough insulin, your body cannot use glucose for fuel, so it breaks down fat instead, and that produces ketones. A few are harmless. A flood of them turns the blood acidic: that is DKA, and it is an emergency. Ketones can climb even when glucose is not very high — see our article on euglycemic DKA — which is why checking ketones, not just glucose, matters when you feel unwell.
When to Check
- Whenever you are sick, especially if you are vomiting or cannot eat. International sick-day guidelines say to always check ketones during illness, and to check glucose and ketones every one to two hours.
- When glucose stays high on a pump. A pump delivers only rapid-acting insulin, and the ADA notes that infusion set problems — a dislodged or blocked set — put pump users at risk of ketosis and DKA.
- When you have symptoms such as nausea, stomach pain, or deep, fast breathing, whatever your glucose says.
Two Ways to Check
Urine ketone strips
You dip a strip in urine, wait the time printed on the pack, and compare the color with the chart: negative, trace, small, moderate or large. Urine strips measure acetoacetate, and on some strips acetone. They are cheap and need no meter.
Their weakness is timing. The 2024 international consensus on hyperglycemic crises notes that urine tests can underestimate ketones early in DKA, because acetoacetate lags behind, and overestimate them later, when the body converts its main ketone into acetoacetate as it recovers. A few medicines, including captopril and valproate, can also cause false-positive urine results.
Blood ketone meters
A blood ketone meter works like a glucose meter — a finger prick onto a ketone strip — and measures beta-hydroxybutyrate (BHB), the main ketone in DKA, as a number in mmol/L. The consensus recommends measuring BHB directly to diagnose and monitor DKA, and international sick-day guidelines prefer blood ketones over urine. In children and teens, testing blood ketones at home picks up ketosis earlier than urine testing and has reduced emergency room visits and hospital stays.
The drawback is cost. The same guidelines acknowledge that blood ketone strips can be unaffordable for many households or not covered by insurance, and say urine strips can be used for sick-day management in that case. Checking with urine strips is far better than not checking at all.
What the Numbers Mean
These bands come from the International Society for Pediatric and Adolescent Diabetes (ISPAD) 2022 sick-day guidelines:
| Blood ketones | Urine strip | What it means |
|---|---|---|
| Under 0.6 mmol/L | Negative or trace | Normal — the target during illness |
| 0.6–0.9 mmol/L | Trace or small | Raised: follow your sick-day plan |
| 1.0–1.4 mmol/L | Small or moderate | Raised: follow your sick-day plan |
| 1.5–2.9 mmol/L | Moderate or large | High: if it stays above 1.5 despite extra insulin and fluids, get urgent medical help |
| 3.0 mmol/L or more | Large | High risk of DKA: get emergency care |
ISPAD writes for children and teens. Adult plans use similar levels, and the 2024 consensus for adults agrees on the top line: a blood BHB of 3.0 mmol/L or more identifies DKA with more than 90% sensitivity and specificity. Your own sick-day plan sets your action points.
Ketones With Normal or Low Glucose
Not eating produces ketones too. ISPAD notes that these “starvation” ketones are usually below 3.0 mmol/L, and when glucose is low or normal during illness, the priority is sugary fluids to keep glucose up. But do not assume ketones with an ordinary glucose reading are harmless — especially if you take an SGLT2 inhibitor or feel very unwell. That is exactly the situation euglycemic DKA describes.
The Rules That Don’t Change
- Never stop insulin when you are sick, even if you are not eating.
- Check glucose and ketones every one to two hours while you are ill.
- On a pump, if ketones reach 0.6 mmol/L or you are vomiting, ISPAD advises leaving automated (closed-loop) mode, following your sick-day rules manually, and changing your cartridge, tubing and infusion site in case they are the problem.
- Get emergency help for ketones of 3.0 mmol/L or more; ketones that stay above 1.5 despite extra insulin and fluids; vomiting that lasts more than two hours; glucose you cannot keep above 70 mg/dL; or confusion, exhaustion, deep fast breathing or severe stomach pain.
Where SweetLife Fits
SweetLife cannot read a ketone meter, but you can record each ketone result in the note on a glucose reading, so it sits right beside your numbers. That makes a sick day much easier to look back on, for you and for your care team. For the full picture of staying safe while ill, see our guide to diabetes sick day rules.
The Short Version
Urine strips measure acetoacetate and can lag behind; blood meters measure beta-hydroxybutyrate, the main ketone in DKA, and are preferred when you can get them. Aim for blood ketones under 0.6 mmol/L. Ketones that stay above 1.5 despite extra insulin and fluids need urgent help, and 3.0 or more means emergency care. Check whenever you are sick, and never stop insulin.
Sources
- Umpierrez GE, Davis GM, ElSayed NA, et al. Hyperglycemic Crises in Adults With Diabetes: A Consensus Report. Diabetes Care. 2024;47(8):1257–1275. doi.org/10.2337/dci24-0032
- Phelan H, Hanas R, Hofer SE, et al. Sick day management in children and adolescents with diabetes. Pediatr Diabetes. 2022;23(7):912–925. doi.org/10.1111/pedi.13415
- American Diabetes Association Professional Practice Committee. 7. Diabetes Technology: Standards of Care in Diabetes—2024. Diabetes Care. 2024;47(Suppl 1):S126–S144. doi.org/10.2337/dc24-S007
Medical Disclaimer: This article is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your physician or qualified healthcare provider with any questions about a medical condition or changes to your diabetes management plan, including medication and insulin dosing. SweetLife is a tracking and logging tool, not a medical device, and does not provide medical advice.