Ketone levels: what's a good number for ketosis
June 10, 2026 · 3 min read
Once you're testing with a blood meter, the obvious question is what number to aim for. The ranges below come from researchers Jeff Volek and Stephen Phinney, who defined nutritional ketosis. The short version: you want to be over 0.5, chasing a bigger number doesn't help, and the "best" reading is lower than most people assume.
The blood ketone ranges
Nutritional ketosis is defined as a blood beta-hydroxybutyrate (BHB) level of 0.5 mmol/L or higher. Volek and Phinney split the range into light, optimal, and deep ketosis — a scale that applies to blood meters, not to urine or breath tests. The ketone-testing research collects the sources behind these numbers.
| Blood BHB (mmol/L) | What it means |
|---|---|
| Below 0.5 | Not in nutritional ketosis |
| 0.5–1.5 | Light nutritional ketosis |
| 1.5–3.0 | Optimal ketosis (Volek & Phinney) |
| 3.0–5.0 | Deep ketosis, e.g. fasting; rarely needed |
| Above ~5 | Uncommon from diet — see the safety note |
Is higher better?
Higher ketones do not mean faster fat loss. Above roughly 1.5 mmol/L, extra ketones add no weight-loss benefit; fat loss is driven by your calorie and carb picture, not by how high the meter reads. Chasing big numbers usually just means eating more fat than you need.
What actually moves the result is the input: net carbs low enough, consistently. Copper Keto Companion tracks that from a spoken meal, so you're managing the lever that drives the number rather than the number itself.
Urine and breath don't use this scale
These mmol/L ranges apply only to blood meters, which read BHB. Urine strips show acetoacetate as a color, and breath meters show acetone as a level or zone, so neither maps cleanly onto the 0.5 to 3.0 blood scale. Use them to confirm ketosis, not to read an exact depth. The testing overview lines the three methods up.
A safety line on high numbers
Very high blood ketones are a different story from deep nutritional ketosis. Readings well above the dietary range — especially with high blood sugar and symptoms like nausea or rapid breathing — can signal diabetic ketoacidosis, a medical emergency that mostly affects people with diabetes. From diet alone in a healthy person, ketones rarely exceed 3. If you have diabetes, discuss any testing and high readings with your doctor. This is general information, not medical advice.
Frequently asked
What is a good ketone level for weight loss? Anything in nutritional ketosis, meaning 0.5 mmol/L or higher; past about 1.5 there's no added weight-loss benefit. Higher numbers don't burn more fat.
Is 1.5 or 3.0 ketones better? Both sit in the optimal range. Neither is better for weight loss; 1.5 to 3.0 is simply where Volek and Phinney mark strong ketosis. Your carb and calorie balance decides fat loss.
Can ketones be too high on keto? From diet alone, rarely — readings above 3 are uncommon without diabetes. Very high ketones alongside high blood sugar is a medical concern, not deeper dieting.