Beta-Hydroxybutyrate (BHB)
Beta-hydroxybutyrate (BHB) is the main ketone your body makes when it burns fat for fuel. It rises with fasting, low-carb eating or too little insulin.
AI-verified against cited sources. Awaiting expert reviewAlso called BHB, 3-HB, BOHBLOINC 29512-1
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What it is
Ketones are a fuel your liver makes from fat when sugar is in short supply, such as during a fast, on a very low-carbohydrate diet, or when the body does not have enough insulin. BHB is the most abundant ketone in the blood. A lab can measure it from a blood sample, and many home meters measure it from a fingerstick. Urine ketone strips measure a different ketone (acetoacetate), so they do not give the same answer.
Why it matters
A small amount of BHB is normal, and higher levels are expected when you fast or eat very few carbohydrates. In someone with diabetes, a high level along with high blood sugar and symptoms can be a sign of diabetic ketoacidosis (DKA), which is a medical emergency. Clinicians also use BHB to help sort out low blood sugar episodes and unexplained acid-base problems.
If it’s low
A low BHB is the usual finding after a recent meal in someone who is not on a very low-carbohydrate diet, and it is not a concern on its own. Clinicians sometimes check BHB with insulin and C-peptide during an episode of low blood sugar, because strong insulin action holds ketone production down.
Common causes
- Eating regularly with a mixed diet, especially soon after a meal
- High insulin levels from insulin, from some diabetes medicines, or (rarely) from an insulin-making tumor
What can help
- A low result on its own usually needs no action
- If you have episodes of low blood sugar, ask your clinician which tests should be done during an episode
If it’s high
A high level means your body is making a lot of ketones. After fasting or on a ketogenic diet this is expected and usually fine. In diabetes, or when you are unwell, ketones can build up and make the blood too acidic (ketoacidosis), so the number should be read together with your blood sugar and how you feel.
Common causes
- Fasting or going a long time without eating
- Very low-carbohydrate (ketogenic) eating
- Too little insulin in people with diabetes (diabetic ketoacidosis)
- Heavy alcohol use with little food
- Vomiting or illness with poor intake, including severe vomiting in pregnancy
- Diabetes medicines called SGLT2 inhibitors, which can raise ketones even when blood sugar looks near normal
What can help
- If you have diabetes, follow your care team's sick-day plan and check your blood sugar when ketones are raised
- Ask your clinician which ketone level should prompt a call or an urgent visit
- If you follow a ketogenic diet, ask whether ketone testing and a safety plan make sense for you, because ketoacidosis is uncommon on these diets but possible
Usual ranges
What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.
For adults: 0.02–0.27 mmol/L. Source: ARUP Laboratories, Labcorp, American Board of Internal Medicine.
- Adults (this one applies)0.02–0.27 mmol/L
Sources: ARUP Laboratories, Labcorp, American Board of Internal Medicine
Ketone cut points in the 2024 hyperglycemic crises consensus report (adults with diabetes)
- Below 0.6: the level the report uses to mark DKA resolutionbelow 0.6 mmol/L
- 0.6 to below 3.0: raised ketones (1.0 to below 3.0 is called mild or moderate ketonemia in the report)0.6 to under 3 mmol/L
- 3.0 and above: level the report links with DKA-range acid-base changes3 and above mmol/L
If this applies to you
BHB means a little more for some people. Open the one that fits you.
Keto or low-carb eating
BHB is a ketone, and the ADA names it as the one to measure in blood. MedlinePlus notes that ketones run higher on a keto diet, usually not high enough to cause ketoacidosis, which makes the blood too acidic. The ADA says very-low-carb eating should be avoided by people taking SGLT2 inhibitor medicines because of the risk of ketoacidosis.
What can affect your result
- Time since your last meal: levels rise the longer you go without eating
- Carbohydrate intake: very low-carbohydrate diets raise BHB
- Insulin: too little insulin raises BHB, while strong insulin action lowers it
- Alcohol, vomiting and pregnancy
- SGLT2-inhibitor diabetes medicines
- Sample type: a lab blood test, a fingerstick meter and a urine strip are different measurements
- Fasting, very low-carbohydrate eating, heavy alcohol use with little food, vomiting and pregnancy can all raise BHB, so the time since your last meal matters.
- Urine ketone strips measure a different ketone (acetoacetate), not BHB, so a strip and a BHB result can disagree, especially early in ketoacidosis.
- Fingerstick ketone meters use a different sample from a lab test. The 2024 consensus report notes concern about how well meters agree with the lab at levels of 5 mmol/L and above.
- ARUP lists serum or plasma, once separated from the cells, as stable for 2 hours at room temperature and 1 week refrigerated, so a sample that waits too long before it is processed may not be accurate.
Any time if you are checking because you feel unwell. If you track ketones for a diet, test at the same time each day (for example before breakfast or at bedtime) so readings are comparable. Reflects the last few hours to days of fuel use rather than a long-term average. In some ketogenic diet trials, participants reached 0.5 mmol/L or more within about a week.
When to talk to a clinician
If you have diabetes and a blood ketone reading of 3.0 mmol/L or higher, or raised ketones with nausea or vomiting, belly pain, fast or deep breathing, fruity-smelling breath, confusion or unusual tiredness, get urgent medical help the same day. Call 911 or your local emergency number if you have trouble breathing or are confused. If you do not have diabetes but follow a ketogenic diet, ask your clinician which levels and symptoms should prompt a call.
Questions you could ask
- Is a lab test, a fingerstick meter or a urine strip the best way for me to check ketones?
- How often, if at all, should I test?
- Which ketone level should make me call you or seek urgent care?
- How should my blood sugar and ketone readings be read together?
- Could any of my current medicines affect my ketone levels?
- Is this result expected given when I last ate?
Questions people ask
Is a high BHB on a keto diet a problem?
Usually not. A 2025 review defines nutritional ketosis as a blood BHB of 0.5 to 5.0 mmol/L, which is a normal response to very low carbohydrate intake. It is different from ketoacidosis, where the blood turns too acidic. Ketoacidosis on a keto diet is uncommon but possible, so talk with your clinician, especially if you have diabetes or take an SGLT2 inhibitor.
How is a blood ketone test different from a urine ketone strip?
A urine strip measures acetoacetate, not BHB. Early in ketoacidosis a strip can look low, and later it can overstate how high ketones are. For this reason the 2024 consensus report recommends measuring BHB directly in blood to check for and follow DKA.
How do I convert BHB between mmol/L and mg/dL?
1 mmol/L is about 10.41 mg/dL. To go from mg/dL to mmol/L, divide by 10.41.
Show the science and sources
Units
- 1 mmol/L = 1 mmol/L
- 1 mmol/L = 10.41 mg/dL
For clinicians and researchers
BHB (3-hydroxybutyrate, 104.1 g/mol) is the most abundant circulating ketone body, formed in the liver from acetoacetate and used as fuel by brain, heart and muscle. The nitroprusside reaction in urine or serum detects acetoacetate but not BHB, so it can lag early in DKA and overstate severity later as BHB is converted back to acetoacetate. The 2024 ADA-led consensus report on hyperglycemic crises recommends direct BHB measurement (venous or capillary) and states that a level of 3.0 mmol/L or higher correlates with acid-base changes with over 90% sensitivity and specificity for DKA; DKA resolution is defined as ketones below 0.6 mmol/L with venous pH of 7.3 or higher or bicarbonate of 18 mmol/L or higher. About 10% of DKA presents with glucose under 200 mg/dL, most often with SGLT2 inhibitors. The differential for raised ketones includes starvation, alcoholic ketoacidosis and ketosis of pregnancy. In hypoglycemia work-ups, the Endocrine Society guideline (2009) advises measuring plasma glucose, insulin, C-peptide, proinsulin and BHB during an episode when endogenous hyperinsulinism is suspected. A 2025 review of non-diabetic hypoglycemia describes insulin-mediated hypoglycemia as glucose of 55 mg/dL or lower with insulin of 3 uU/mL or higher, C-peptide of 0.6 ng/mL or higher, proinsulin of 5 pmol/L or higher and BHB of 2.7 mmol/L or lower. A 2025 review defines nutritional ketosis as blood BHB of 0.5 to 5.0 mmol/L. Reference intervals are lab and method specific (ARUP 0.02 to 0.27 mmol/L; Labcorp 0.2 to 2.8 mg/dL; ABIM below 0.4 mmol/L).
LOINC 29512-1 (primary), 6873-4, 35255-9, 104816-4, 66441-7. Specimen: serum-or-plasma.
Sources
- Beta-Hydroxybutyric Acid (test 0080045), ARUP Laboratories
- β-Hydroxybutyrate (test 503610), Labcorp
- ABIM Laboratory Test Reference Ranges (January 2026), American Board of Internal Medicine (2026)
- Hyperglycemic Crises in Adults With Diabetes: A Consensus Report, Diabetes Care (American Diabetes Association and partner societies) (2024)
- 6. Glycemic Goals, Hypoglycemia, and Hyperglycemic Crises: Standards of Care in Diabetes-2026, American Diabetes Association (Diabetes Care) (2026)
- The role of beta-hydroxybutyrate testing in ketogenic metabolic therapies, Frontiers in Nutrition (2025)
- Ketones in Blood, MedlinePlus, National Library of Medicine
- Evaluation and management of adult hypoglycemic disorders: an Endocrine Society Clinical Practice Guideline, Journal of Clinical Endocrinology & Metabolism (2009)
- Pancreatic Neuroendocrine Tumors: Diagnostic Pitfalls of Non-Diabetic Severe Hypoglycemia: Literature Review and Case Report, Diagnostics (Basel) (2025)
- 3-Hydroxybutyric Acid (PubChem compound 441), PubChem, National Library of Medicine
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.