What is the normal level of blood ketones (ketone bodies)?

From the Guidelines

Normal blood ketone levels are typically considered to be less than 0.5 mmol/L, as stated in the 2023 guidelines and recommendations for laboratory analysis in the diagnosis and management of diabetes mellitus 1. When evaluating blood ketone levels, it's essential to consider the context and individual circumstances.

• In healthy individuals, blood ketone levels usually range from 0.05 to 0.5 mmol/L when fasting.
• During nutritional ketosis, such as when following a ketogenic diet, levels may rise to 0.5-3.0 mmol/L, which is generally considered safe.
• However, when blood ketone levels exceed 3.0 mmol/L, this may indicate ketoacidosis, a potentially dangerous condition that requires medical attention, particularly in people with diabetes. Key factors to consider when interpreting blood ketone levels include:
• The presence of diabetes or a history of diabetic ketoacidosis (DKA)
• The use of certain medications, such as sodium–glucose cotransporter 2 (SGLT2) inhibitors
• Symptoms of ketosis, such as abdominal pain or nausea According to the guidelines, individuals who are prone to ketosis should measure ketones in urine or blood if they have unexplained hyperglycemia or symptoms of ketosis and implement sick day rules and/or seek medical advice if urine or blood ketones are increased 1.
• For diabetic individuals monitoring ketones, levels below 0.6 mmol/L are considered normal,
• 0.6-1.5 mmol/L indicate a need for closer monitoring,
• and levels above 1.5 mmol/L often require medical consultation. Ketones are produced when the body burns fat for energy instead of carbohydrates, which happens during fasting, intense exercise, or when carbohydrate intake is very low 1. Regular monitoring of ketone levels is especially important for people with type 1 diabetes or those following therapeutic ketogenic diets to ensure they remain within safe ranges.

From the Research

Normal Blood Ketone Levels

• Normal blood ketone levels are typically considered to be less than 0.6 mmol/L 2
• In type 1 diabetic patients using continuous subcutaneous insulin infusion (CSII), normal capillary blood ketone levels are usually below 0.3 mmol/L 2
• A study found that 81.3% of capillary ketone measurements in type 1 diabetic patients on CSII were below 0.1 mmol/L, while 13% were between 0.1-0.2 mmol/L, and 3.7% were between 0.2-0.3 mmol/L 2
• Another study suggested that a maximum ketone level of 0.8 mmol/L or higher may be associated with an increased risk of diabetic ketoacidosis (DKA) in type 1 diabetes patients using sodium-glucose cotransporter inhibitors (SGLTi) 3

Factors Affecting Blood Ketone Levels

• Blood ketone levels can increase during fasting, prolonged exercise, and in certain physiological states such as pregnancy and the neonatal period 4, 5
• Diabetes is a common pathological cause of elevated blood ketones, particularly in diabetic ketoacidosis (DKA) 4
• The use of a ketogenic diet (KD) can also increase blood ketone levels, as the diet is designed to induce a state of ketosis 5, 6

Measurement of Blood Ketone Levels

• Capillary blood ketone testing can be used to monitor ketone levels in diabetic patients 3, 2
• The nitroprusside test is a commonly used method for detecting ketones in blood and urine, but it only detects acetoacetate and not 3-beta-hydroxybutyrate (3HB), which is a more reliable indicator of ketone body levels 4
• Quantitative tests for 3HB are available and can provide a more accurate measurement of ketone levels 4