Quick answer: You can check ketone levels with blood meters, breath analyzers or urine strips. Blood meters measure beta-hydroxybutyrate directly and are the most accurate but cost more. Breath analyzers measure acetone and need no strips. Urine strips are cheap and easy but may become less reliable once your body adapts to keto.
Key takeaways
Testing ketones shows whether you are in ketosis and how different foods affect you.
Blood meters are the most accurate, breath analyzers are reusable but less precise, and urine strips become less useful as your body adapts.
People with diabetes use ketone testing to watch for ketoacidosis, and very high ketones with high blood sugar or vomiting need urgent care.
Why monitor ketones?
Testing shows whether you are in ketosis and how foods affect you. See what is ketosis.
Blood ketone meters
A finger-prick drop of blood measures beta-hydroxybutyrate. The most accurate option, but strips add cost.
Breath ketone analyzers
Measure acetone in your breath. Reusable with no strips, but less precise.
Urine ketone strips
Inexpensive and simple, but urine ketones may fall as your body becomes better at using ketones, so they become less useful over time.
Safety for people with diabetes
People with diabetes use ketone testing to watch for ketoacidosis. Very high ketones with high blood sugar, nausea or vomiting need urgent care.
Healthy aging lens
Tracking how foods affect you builds awareness. Pair ketone tests with measuring your results.
What the research shows
Ketone testing methods have been compared in research settings.
When to test ketones (Urbain 2016, monitoring study). 12 healthy adults in their sixth week of a ketogenic diet tested urine 8 times and blood 18 times over 24 hours. Blood beta-hydroxybutyrate was lowest around 10 a.m. (0.33 mmol/L) and highest around 3 a.m. (0.70 mmol/L), and urine strips detected ketosis most reliably (over 90% of the time) in early-morning and after-dinner samples. A limitation is the small group of healthy volunteers.
Six weeks of keto in healthy adults (Urbain 2017, before-and-after study). 42 healthy adults followed a ketogenic diet (about 72% fat, 21% protein and 8% carbohydrate) without calorie limits for 6 weeks. They lost about 2 kg, split equally between fat and lean mass. Peak power dropped 4%, LDL cholesterol rose about 11%, and insulin fell 22%. A limitation is that there was no control group, so changes can’t be fully separated from other factors.
Strength of the evidence: Blood tests are the most accurate; urine strips work best early in keto and at certain times of day, and breath meters vary by brand.
When to see a naturopathic doctor
It may be time to see a naturopathic doctor if you have diabetes or take insulin, sulfonylureas or SGLT2 inhibitors (risk of low blood sugar or ketoacidosis), or if you take blood pressure medication or diuretics. The same is true if you have kidney, liver, gallbladder or pancreas disease, or high cholesterol, if you are pregnant, breastfeeding, or have a history of disordered eating, or if you want a keto plan tailored to your labs and goals.
See a medical provider promptly for nausea and vomiting, abdominal pain, confusion, fruity-smelling breath with rapid breathing, or very high blood sugar or ketone readings, which can signal ketoacidosis.
Want a keto plan that’s safe for your health?
A free 15-minute consultation with Dr. Kneessi. No cost, no obligation. In-office in Odenton, MD or by telehealth.
Questions to bring to your clinician
These questions can help you get the most out of your next visit.
Which ketone testing method makes the most sense for me?
What might my ketone readings be telling us, given my health history and symptoms?
Which other labs would be worth pairing with my ketone readings to get a clearer picture?
When would it make sense to recheck my ketone readings, and what could I work on in the meantime?
Frequently asked questions
What is the most accurate way to test ketones?
Blood ketone meters.
Are urine strips accurate?
They’re useful early but less reliable later.
What do breath analyzers measure?
Acetone in your breath.
When should I worry about high ketones?
If you have diabetes and high blood sugar, nausea or vomiting, seek care.
Sources
- Anderson JC, et al. Measuring ketone bodies for the monitoring of pathologic and therapeutic ketosis. Obes Sci Pract 2021. PMID: 34631141. https://pmc.ncbi.nlm.nih.gov/articles/PMC8488448/
- Laffel L. Ketone bodies: a review of physiology, pathophysiology and application of monitoring to diabetes. Diabetes Metab Res Rev 1999. PMID: 10634967. https://pubmed.ncbi.nlm.nih.gov/10634967/
- Anderson JC. Measuring breath acetone for monitoring fat loss: Review. Obesity (Silver Spring) 2015. PMID: 26524104. https://pmc.ncbi.nlm.nih.gov/articles/PMC4737348/
- Dhatariya KK, et al. Diabetic ketoacidosis. Nat Rev Dis Primers 2020. PMID: 32409703. https://pubmed.ncbi.nlm.nih.gov/32409703/
- MedlinePlus: Ketones in Blood
- MedlinePlus: Ketones in Urine
- Urbain P, Bertz H. Monitoring for compliance with a ketogenic diet: what is the best time of day to test for urinary ketosis? Nutr Metab (Lond) 2016. PMID: 27822291. https://pubmed.ncbi.nlm.nih.gov/27822291/
- Urbain P, et al. Impact of a 6-week non-energy-restricted ketogenic diet on physical fitness, body composition and biochemical parameters in healthy adults. Nutr Metab (Lond) 2017. PMID: 28239404. https://pubmed.ncbi.nlm.nih.gov/28239404/
This article is for educational purposes only and is not medical advice. It does not replace an individual evaluation. Talk with your healthcare provider before starting supplements or changing medications, especially if you are pregnant, nursing, or managing a health condition.
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