Blood ketone meters are devices that allow you to test for ketones circulating in your body. These are chemicals produced by the liver when the body needs to burn fat as fuel.
You could use a blood ketone meter if you’re following a ketonenic diet and want to ensure you’re in ketosis.
Blood Ketone Meters for Testing at Home
To test the ketones in your blood, you will need a blood ketone meter and a kit that includes the lancet pen and ketone test strips. These meters also read blood glucose test strips. Results download to your computer.
Ketone Test Strips
You must purchase ketone test strips as glucose test strips won’t test for ketones. You will also need to use blood from your fingertip rather from an alternate site.
The strips are for one time use only. They can be the expensive part of testing, especially if they are not covered by your insurance.
Follow these tips and precautions when purchasing test strips:
- Be sure to get the correct test strips for the correct meter (they are not interchangeable).
- Pay attention to expiration dates on the strips, both when you receive your purchase and when you test your blood. Expired strips will not give accurate results.
- The Food and Drug Administration (FDA) warns against buying previously-owned test strips.
- While it may be legal, you risk getting a product that hasn’t been properly stored and could be expired.
- The FDA also warns against purchasing strips that have not been cleared by the agency for sale in the United States.
How to Test Your Blood for Ketones
- Load a needle into the lancet pen according to package directions.
- Wash your hands with soap and dry them well.
- Remove a test strip from the packaging and insert it into the meter.
- Place the lancet pen on the side of your fingertip and push the button.
- Gently squeeze your finger to get a drop of blood. You will need a large drop to load the strip properly. After you do it two or three times, you’ll get a sense of how much blood you need. With the Precision meter, you need a bigger drop of blood than when you are testing blood glucose (even using the same meter).
- Touch the end of the test strip to the drop of blood until it fills the little opening and the meter registers.
- Wait for the meter to give you a reading (just a few seconds).
- Record your results. Discard the test strip.
Ketone Testing for Ketogenic Diets
If you have normal blood glucose, your blood ketones may be the highest in the morning after your overnight fast. However, many people report that their ketones rise over the course of the day. If you want to track your blood ketones day-to-day, picking one time of day and sticking with it will give you the best comparison.
Some factors besides the overall diet which may cause fluctuations include exercise and consuming fats with medium-chain triglycerides, such as coconut oil or MCT oil. And, of course, eating something (usually high in carbs) that knocks you out of ketosis will cause your ketone level to plummet.
How to Interpret the Results for Ketogenic Diets
If you are new to ketogenic diets and have a goal of nutritional ketosis (often defined as between 0.5 and 3 mmol/L), know that it can take two to four weeks to get consistently into this range.4 It often takes a fair amount of tweaking to figure out what you can and can’t eat, even for people who are low-carb veterans.
The ketone meter was developed to alert people with insulin-dependent diabetes to the signs of dangerous diabetic ketoacidosis. However, if you do not have diabetes and are on a ketogenic diet, you are using it for a different reason entirely. In this case, high ketones are not a sign of high blood glucose, are not caused by protein breakdown, and are not toxic.
For detailed information about nutritional ketosis, check out the books by Jeff Volek and Stephen Phinney: The Art and Science of Low Carbohydrate Living and The Art and Science of Low Carbohydrate Performance.