One of the biggest challenges is to determine when people are in ketosis.

It is commonly said to be 0.5 mmol/L.

  • <0.3 mmol/L BHB: not in ketosis
  • 0.3–0.49 mmol/L BHB: borderline ketosis
  • ≥0.5 mmol/L BHB: in ketosis

This system is not ideal, because we don’t know precisely when ketosis occurs.

There is no data objectively confirming a ketosis cutoff point.

However, 0.5 mmol/L of serum BHB is commonly used as a cutoff by keto researchers (McKenzie et al., 2017; Harvey et al., 2018).

However, some researchers use 0.3 mmol/L (Wilson et al., 2017), while others use 1 mmol/l (Burstal et al., 2018).

Take home note? There is no objective set point. Most people online however will tell you 0.5 mmol/L which is a good starting point and perhaps something to aim at if you want a basic idea.

As long as you are in a deficit, and fat loss is your objective, the exact level does not matter much, if at all.