Blood Ketone Meters

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Blood ketone meter and blood ketone meter test strips

A blood ketone meter is a medical meter that measures your blood ketone levels using ketone test strips. The blood ketone meter works with a finger prick blood sample, which is obtained using a lancet or lancing device.

A blood ketone meter is used by diabetics and by people on ketogenic diets where they want to monitor their ketone levels to see if they are in ketosis. 

Blood ketone meter accuracy 

Using a blood ketone meter is the most accurate way to monitor blood ketone levels. They are more accurate than urine ketone test strips or breath ketone meters at detecting ketosis but you are required to obtain a blood sample so you may find a combination of urine and blood ketone tests works best for you.

Choose from a combined blood glucose and ketone meter or just a blood ketone meter:

Blood ketone testing – Frequently asked questions

Blood ketone testing is the most accurate way to measure your body’s ketone levels, whether you're following a ketogenic diet, practising intermittent fasting, or managing diabetes. Unlike urine ketone test strips, blood ketone meters measure beta-hydroxybutyrate (BHB), the primary ketone used for energy.

In this FAQ section, we answer the most common questions about blood ketone testing, including how to use a meter, what your results mean, and how to optimise your ketone levels for fat burning or metabolic health.

How do I use a blood ketone meter?

  • Wash hands and dry them completely.
  • Insert a ketone test strip into the meter.
  • Prick your fingertip with the lancing device.
  • Place a small drop of blood onto the test strip.
  • Wait for the meter to display your ketone reading.

It is always important to read the instructions before you start as different ketone meter instructions may vary slightly.

How long does it take to show ketones on a keto diet?

It does vary between individuals but most people start producing ketones within 2–4 days of strict carb restriction. If you don’t see results within a week, you may need to adjust your macros.

Do I need to be in deep ketosis for weight loss?

Not necessarily. Mild to moderate ketosis (0.5 – 1.5 mmol/L) is often enough for fat burning. Weight loss depends on lots of factors including caloric intake, activity levels, and metabolic health, not just ketone levels.

Can exercise affect my ketone readings?

Yes. After a workout, ketone levels may temporarily drop as your body burns them for energy. Testing a few hours later may show higher levels again.

Will ketone test strips show results if I’m doing intermittent fasting?

Yes! Fasting naturally increases ketone production. If you are fasting correctly, you should see ketone levels rise after several hours without food.

Can I use ketone test strips while fasting?

Yes! Many people use ketone test strips to track ketone levels during intermittent fasting or extended fasts. Levels typically increase after several hours without food.

What is blood ketone testing?

Blood ketone testing measures beta-hydroxybutyrate (BHB), the most reliable ketone body in the bloodstream. It is used by keto dieters, athletes, and diabetics to monitor ketosis and metabolic health.

How is blood ketone testing different from urine ketone testing?

  • Blood ketone tests measure BHB, the primary ketone used for energy.
  • Urine ketone strips detect acetoacetate, which may decline as you become keto-adapted.
  • Blood testing provides more accurate, real-time ketosis tracking.

How often should I test my blood ketones?

  • Keto dieters: Once a day or a few times per week.
  • Athletes & biohackers: Before and after workouts or meals.
  • Diabetics: As advised by a doctor, especially if blood sugar is high.

What is the best time to test blood ketones?

  • Morning (fasted) – Gives a baseline reading.
  • Before meals – Shows if you're maintaining ketosis.
  • After eating – Helps track food impact on ketones.
  • Post-exercise – Can indicate fat-burning efficiency.

Why are my blood ketone levels low despite eating keto?

  • Your body may be efficiently using ketones for fuel rather than accumulating them in the blood.
  • You may be eating too much protein, which can be converted into glucose.
  • If you're new to keto, your body may still be adjusting.

Can hydration affect blood ketone levels?

Hydration primarily affects urine ketone tests. Blood ketone levels remain relatively stable regardless of fluid intake.

Hydration can have some effect on blood ketone levels, although it's less direct than with urine ketones. Here's why:

  • Dilution Effect: In a well-hydrated state, blood volume increases, which can slightly reduce ketone concentration (though not as dramatically as urine ketones).
  • Fat metabolism influence: Dehydration may increase stress hormones like cortisol, which can lead to a temporary rise in blood sugar, potentially lowering ketone production.
  • Liver function: Hydration supports liver function, which is crucial for producing ketones from fat. Dehydration could slow ketone production.

So, while hydration doesn't directly "wash out" blood ketones like it does in urine, it can still impact ketone production and metabolism.

Do high blood ketones mean I’m burning more fat?

Not necessarily. Fat loss depends on caloric intake and energy expenditure, not just high ketone levels. Moderate ketosis (1.5–3.0 mmol/L) is sufficient for fat-burning.

Can diabetics use blood ketone testing?

Yes. Blood ketone testing is important for diabetics, especially those with Type 1 diabetes, to detect diabetic ketoacidosis (DKA). If ketones are high and blood sugar is elevated, seek medical help immediately.