Blood Ketone Meters: BHB Readings and Ranges

A blood ketone meter reads beta-hydroxybutyrate (BHB), the main ketone in your blood, from a finger-prick drop and reports it in mmol/L, which makes it the most direct home test for ketosis and also the most expensive per test.

On this page

• What a blood meter measures
• What mmol/L means
• Nutritional ketosis vs ketoacidosis
• What a reading can and cannot tell you
• What blood testing costs
• How to take a reading
• Who should use one under a doctor
• Related

What a blood meter measures

Your liver makes three ketone bodies: acetoacetate, BHB and acetone (StatPearls, Ketogenesis). BHB is the one that travels in your blood as fuel, and it is what a blood ketone strip reads.

Your body does use these ketones. After weeks of fasting, BHB and acetoacetate replaced glucose as the brain's main fuel in a classic study (Owen et al., 1967).

A blood ketone meter looks and works like a glucose meter. It takes its own ketone strips, which are not the same as glucose strips. Some meters read both, with the right strip for each (video 8wOheKcBEd8).

A glucose reading does not tell you whether you are in ketosis. KetoDick makes this point about his own blood-glucose testing (video xyEZL0HuejI).

What mmol/L means

Blood ketones are reported in millimoles per litre (mmol/L). It is a measure of how many BHB molecules are in a set amount of blood. A higher number means more BHB in your blood at that moment.

Three things move the number during the day:

• What you ate and when. A carb-heavy meal can drop it.
• How long since you last ate. Readings often rise with time since a meal.
• Exercise. Hard activity can push it up or down for a while.

So one reading is a snapshot, not your "level." If you compare days, test at the same time and in the same conditions.

Nutritional ketosis vs ketoacidosis

The same unit, mmol/L, describes two very different states:

Insulin is one of the hormones that keeps ketone production in check (StatPearls, Ketogenesis). That brake is what separates the two states. The clinical overview of the ketogenic diet covers how nutritional ketosis differs from DKA (StatPearls, The Ketogenic Diet), and a review of ketone monitoring in diabetes compares the ketone levels seen in each (Laffel, 1999).

This guide does not give a target number. Meter makers print reference ranges with their strips, and if you have diabetes, your care team sets the level that needs action. More detail: Ketosis vs Ketoacidosis.

KetoDick on this: he defines a ketogenic diet by its outcome: blood ketones within the nutritional-ketosis range, whatever foods get you there (video ffwBPoKxlDI). He says that a healthy person with normal kidney function cannot reach a dangerous ketone level through diet alone (video 8wOheKcBEd8).

What a reading can and cannot tell you

Higher is not better for fat loss. When 17 men switched to a ketogenic diet at the same calories in a metabolic ward, body-fat loss slowed after the switch (Hall et al., 2016). Ketones in your blood can also come from ketone drinks, which add ketones without burning any of your own fat. See Does ketosis mean you are burning fat?, Exogenous ketones and weight loss and Chapter 2: How Fat Loss Actually Works.

What blood testing costs

The meter is a one-off cost. The strips are the ongoing cost, and they add up.

Prices have changed since 2017; check current ones before you decide.

KetoDick on this: he suggests a blood meter mainly for people several months to years in, when urine strips stop turning positive (videos GojQvo_2GS0, 8wOheKcBEd8). Even then, he says that if you are six months in, eating the same way and feeling the same, you are probably still in ketosis and do not need to pay for blood testing (video xyEZL0HuejI).

How to take a reading

Follow your meter's instructions. The general steps:

1. Wash and dry your hands. Food or sugar on your fingers can affect any finger-prick test.
2. Put a ketone strip (not a glucose strip) in the meter.
3. Prick the side of a fingertip with the lancet.
4. Touch the drop to the strip and wait for the number.
5. Write down the reading, the time, and what and when you last ate.

If you want to learn from the numbers, test at the same time each day, such as before breakfast, for a week or two. Then stop, unless a doctor has asked you to keep going.

Who should use one under a doctor

For some people, a blood ketone meter is a safety tool, not a diet gadget. Talk to your doctor and get a written plan if you:

• Have type 1 diabetes, or type 2 diabetes on insulin or other glucose-lowering medication. Ketone monitoring in diabetes is used to catch ketoacidosis early (Laffel, 1999). Low-carb eating can also change how much medication you need: in one non-randomised trial, the low-carb group used less diabetes medication than usual care (Hallberg et al., 2018). See Medications and Keto.
• Have kidney disease or risk for it. KetoDick says that for a diabetic or someone with kidney issues, a dark testing strip could point to a problem (video GojQvo_2GS0).
• Are pregnant or breastfeeding. Ketone targets in pregnancy are a decision for your obstetric team.

See Who Should Talk to a Doctor Before Starting Keto.

Related

• Chapter 8: Testing for Ketosis: Urine, Blood and Breath
• Urine Ketone Strips
• Breath Ketone Testing
• Do You Need to Test Ketones at All?
• What Ketosis Is: Ketone Bodies, BHB and Your Liver
• Blog: Is there an optimal ketone level for weight loss?
• Videos: Three ways to test for ketosis · What foods are banned on keto? · Common beginner questions

Last verified: 2026-10-31