Beta-Hydroxybutyrate Unit Converter
Beta-Hydroxybutyrate Unit Converter
Convert beta-hydroxybutyrate between mg/dL, mmol/L and mg/L, with the DKA thresholds and why urine ketones can improve while the patient is still acidotic.
Beta-Hydroxybutyrate converter
mg/dL ⇄ mmol/LBeta-hydroxybutyrate 32 mg/dL
Formula and conversion factor
mg/dL = mmol/L × 10.41
mg/L = mg/dL × 10
- 0.0961
- derived from the molecular mass of 3-hydroxybutyric acid, 104.10; one mg/dL is 0.01 g/L, and 0.01 ÷ 104.10 gives 96.1 µmol/L
- 10.41
- the reciprocal — a mmol/L figure multiplied by 10.41 gives mg/dL, so the 3.0 mmol/L diagnostic threshold is 31 mg/dL
- mg/L
- ten times the mg/dL figure; used by some send-away assays
- not acetoacetate
- beta-hydroxybutyrate is technically a hydroxy acid rather than a ketone, which is why the nitroprusside reaction cannot see it
Worked example
Beta-hydroxybutyrate 32 mg/dL
32 × 0.0960615 = 3.07 mmol/L
32 × 10 = 320 mg/L
Above the 3.0 mmol/L threshold used to support a diagnosis of ketoacidosis, and well above the fed adult range of 0–6 mg/dL
Thresholds in both units
| mmol/L | mg/dL | |
|---|---|---|
| Fed adult | < 0.6 | < 6 |
| Resolution of DKA | < 0.6 | < 6 |
| Prolonged fasting or ketogenic diet | 0.5 – 3.0 | 5 – 31 |
| Ketosis warranting review in diabetes | ≥ 1.5 | ≥ 16 |
| Supports ketoacidosis with acidosis | ≥ 3.0 | ≥ 31 |
Blood beta-hydroxybutyrate against urine ketones
| Blood BHB | Urine nitroprusside | |
|---|---|---|
| What it detects | Beta-hydroxybutyrate, the dominant ketone in DKA | Acetoacetate and acetone only |
| Behaviour during treatment | Falls as ketosis resolves | Can rise or plateau as BHB is converted back to acetoacetate |
| Use for monitoring resolution | Recommended | Misleading — may look worse while the patient improves |
| Lag after recovery | None | Ketonuria persists for hours to days |
Why urine ketones mislead in ketoacidosis
Beta-hydroxybutyrate is reported in mmol/L in most of the world and in mg/dL in the United States, with some send-away assays using mg/L. The factor of 0.0961 mmol/L per mg/dL derives from a molecular mass of 104.10. Holding the two diagnostic numbers in both conventions is worth the effort: 3.0 mmol/L, the threshold that supports a diagnosis of ketoacidosis, is 31 mg/dL, and 0.6 mmol/L, the threshold for resolution, is 6 mg/dL.
The clinically important fact about this molecule is what does not measure it. Urine ketone sticks use the nitroprusside reaction, which detects acetoacetate and, weakly, acetone — but not beta-hydroxybutyrate, which is technically a hydroxy acid rather than a ketone. In diabetic ketoacidosis the highly reduced intracellular environment drives the equilibrium towards beta-hydroxybutyrate, which can account for the large majority of circulating ketones. Urine testing therefore understates the severity of the illness exactly when severity matters most.
The same chemistry produces a more dangerous artefact during treatment. As the patient recovers and the redox state normalises, beta-hydroxybutyrate is converted back to acetoacetate — which is what the stick detects. Urine ketones can therefore rise, or stay stubbornly positive, in a patient whose acidosis is resolving, and ketonuria persists for hours to days after the blood has cleared. Bedside blood beta-hydroxybutyrate is the measurement that should be used to monitor resolution, and national guidelines now specify it.
Raised levels are not confined to diabetes. Alcoholic ketoacidosis characteristically produces a very high beta-hydroxybutyrate to acetoacetate ratio, so urine ketones can be near-negative in a profoundly acidotic patient; starvation ketosis and ketogenic diets raise it more modestly. SGLT2 inhibitors deserve particular attention, because they can precipitate euglycaemic ketoacidosis in which the glucose is normal or only mildly raised. A patient on one of these drugs who is acidotic needs a ketone measurement regardless of the glucose.
Frequently asked questions
How do I convert beta-hydroxybutyrate from mg/dL to mmol/L?
Multiply by 0.0961, a factor derived from its molecular mass of 104.10. A level of 32 mg/dL is 3.07 mmol/L. To go the other way, multiply the mmol/L figure by 10.41.
What level indicates diabetic ketoacidosis?
A blood beta-hydroxybutyrate of 3.0 mmol/L (31 mg/dL) or above supports the diagnosis, but only alongside acidosis and hyperglycaemia or known diabetes. Resolution is defined by a level below 0.6 mmol/L (6 mg/dL).
Why do urine ketone sticks miss beta-hydroxybutyrate?
The nitroprusside reaction detects acetoacetate and, weakly, acetone. Beta-hydroxybutyrate is chemically a hydroxy acid rather than a ketone and does not react at all, so urine testing understates ketoacidosis, where beta-hydroxybutyrate is the dominant ketone.
Why can urine ketones worsen while a patient with DKA is improving?
As the acidosis resolves, beta-hydroxybutyrate is converted back to acetoacetate, which is the molecule the stick detects. Urine ketones can therefore rise or plateau during successful treatment, and ketonuria persists for hours to days after the blood has cleared.
Can ketoacidosis occur with a normal glucose?
Yes. SGLT2 inhibitors can precipitate euglycaemic diabetic ketoacidosis, in which the glucose is normal or only mildly raised while the patient is acidotic. Alcoholic and starvation ketoacidosis also occur without hyperglycaemia. Measure ketones on the clinical picture, not on the glucose.
Related calculators
References
- Joint British Diabetes Societies for Inpatient Care. The Management of Diabetic Ketoacidosis in Adults. JBDS 02. 2023.
- Dhatariya KK. Defining and characterising diabetic ketoacidosis in adults. Diabetes Res Clin Pract. 2019;155:107797.
- Umpierrez GE, Davis GM, ElSayed NA, et al. Hyperglycaemic crises in adults with diabetes: a consensus report. Diabetologia. 2024;67(8):1455–1479.