Ketosis and ketoacidosis

You often hear that keto puts you into ketosis and that ketoacidosis, the dangerous complication of diabetes, is then only a step away. The names sound alike and ketones do rise in both. They differ in insulin and in the acidity of the blood, though, and those two decide the danger.

What ketosis is and how you get there is covered in the guide The keto diet for beginners.

What keeps ketones in check

When you eat few carbs, insulin falls and the liver starts making ketones from fat. It never falls to zero, though. The insulin your own body produces is what protects it from ketoacidosis, which is why blood sugar and blood pH stay within normal limits (Gershuni et al., 2018).

In diabetic ketoacidosis insulin is missing, or so low that it can hold back neither glucose production nor ketone production. Blood sugar climbs, ketones rise unchecked and the blood turns acidic (Umpierrez et al., 2024).

Where the difference shows

The two ketone ranges overlap between 3 and 5, so ketoacidosis is never diagnosed on ketones alone; acidic blood has to be there too. In practice the gap is wide, as ketones in ketoacidosis run at five to ten times the levels seen in nutritional ketosis (Gershuni et al., 2018).

Who needs to be careful

People with type 1 diabetes make no insulin of their own, so the natural brake is missing. For them keto should only ever be done alongside the doctor who manages their insulin.

The second group is anyone taking SGLT2 tablets for diabetes, such as dapagliflozin or empagliflozin. The 2024 report from the diabetes societies lists very low-carbohydrate diets and prolonged fasting among the risk factors for ketoacidosis with these drugs. With them, ketoacidosis can turn up with blood sugar below 200 mg/dl. About 1 in 10 cases look like this, and the tablets themselves are behind most of them (Umpierrez et al., 2024). If you take them, talk to your doctor before you start keto. The European Medicines Agency's warning about the same tablets is in the guide Keto flu.

Anyone with diabetes who gets nausea, vomiting and fast, deep breathing should check their blood ketones and get help straight away.

How to measure ketones

A blood meter reads beta-hydroxybutyrate in mmol/l, the same measure used in hospital, and according to the 2024 report handheld finger-prick meters come close to a laboratory test in precision.

Urine strips cost less but have a weak spot on keto. As the body gets used to ketosis, the kidneys hold on to more ketones, so the strip shows fewer than are actually in the blood (Fante et al., 2025). If you have been on keto for some time, a faint strip does not necessarily mean you have dropped out of ketosis.