Ketone levels while fasting
Blood ketones expected at each hour of fasting, drawn from fasting studies. Your own meter has the final say.
Ketone levels while fasting at each milestone
| Hours since last meal | Expected blood ketones (mmol/L) | Middle | Stage |
|---|---|---|---|
| 12 h | 0.2–0.5 | 0.3 | Light ketosis |
| 16 h | 0.2–0.8 | 0.4 | Light ketosis |
| 18 h | 0.3–1 | 0.5 | Light nutritional ketosis |
| 24 h | 0.5–1.5 | 0.9 | Light nutritional ketosis |
| 36 h | 0.8–2 | 1.3 | Nutritional ketosis |
| 48 h | 1.2–2.5 | 1.7 | Nutritional ketosis |
| 72 h | 2–4 | 2.8 | Deep ketosis |
Assumes a moderate meal, no exercise and no keto adaptation. The calculator adjusts the hours to match your answers.
At 16 hours, expect 0.25–0.8 mmol/L, a light ketosis level.
Hours to ketosis, based on your last meal
| Carbs in the last meal | Hours to 0.5 mmol/L | Hours to 1 mmol/L |
|---|---|---|
| High carb | 21 h | 32 h |
| Moderate | 17 h | 28 h |
| Low carb | 14 h | 25 h |
| Keto | 11 h | 22 h |
Values sit in the middle of the expected range, with no exercise and no keto adaptation.