Keto Testing: A Guide to Testing Your Ketones & Glucose Levels

Take the Guesswork Out of Ketosis

If you want to know whether you are in ketosis or what level of ketosis you are in, you need to test. Testing is the only way to really know. And while there are various methods of testing, blood ketone monitors, such as your Keto-Mojo meter, are considered the gold standard for determining if you are in ketosis, at what level, and what your blood glucose level is. Glucose testing is commonly conducted to help with diabetes management, but it’s also useful for ketonians because it can reveal “trigger foods,” or foods that spike your glucose and thus may adversely affect your ketone levels. But when is the best time to test?

Best Times to Test Your Ketones & Glucose

Testing ketones and glucose at roughly the same time each day is important for tracking your progress. So, the very best time to test is when it is convenient for you on a regular basis. If you choose a time that’s convenient for you to test daily, you’ll be more likely to continue testing on time, and thus be able to compare your results to prior days at the same time. However, since sleep and meals can skew test results, certain times are better than others.

Here’s when we like to test:

Test in the Morning While Fasted

Testing before you ingest anything but after you’ve been awake awhile helps you avoid the “dawn effect” (an early-morning increase in blood sugar/glucose caused by a natural rise in cortisol before you wake). In the morning, glucose will generally be higher and ketones are generally at their lowest. You can learn more about the dawn effect here.

A fasted test result will give you a good baseline to compare over time. But just how long to wait after you’ve risen may depend on your metabolic state or condition. For someone without insulin resistance, testing an hour after waking will generally provide a good fasted baseline. But for someone who is insulin resistant, which causes elevated levels of glucose in the blood, it may be better to wait 2-3 hours for your fasted baseline, giving your body more time to adjust to the cortisol spike. The best way to determine the ideal time for you is by testing your glucose consecutive days at the same intervals after waking: 1 hour, 2 hours, 3 hours. This will help you understand how long it takes for your glucose to level out.

If your ketones are 1 mmol/L or higher during your anticipated lowest levels of the day, that’s good news; it means you are most likely in a deep state of ketosis!

Test Before Lunch or Dinner

For the most insightful ketone readings, test right before lunch or dinner, at least 2-3 hours after you’ve eaten any other food or drink (other than water). It’s important wait 2-3 hours after eating because consumption of almost any food, keto-friendly or otherwise, will cause your glucose to go up and your ketone levels to fall a bit. Thus, testing well between meals ensures you get a truer reading of your progress.

Testing Before and After Meals to Determine Food Sensitivities

Although we just recommended that you do not test after you’ve eaten, there is one reason you may want to: testing just before a meal or particular food and then 60 minutes and 3 hours afterward is a great way to find out how your body responds to various foods, snacks, and drinks you have consumed. Advanced users may want to add additional tests at 30 minutes and 2 hours. You can learn more about testing for food sensitivities here.

When testing for food sensitivities, please note that glucose strips are a better indication of food reactions because glucose fluctuates faster than ketones. For example, glucose reaches its peak one hour after eating, while ketones take much longer to generate.

Testing Your GKI

The Glucose Ketone Index or GKI gives you a better overall view of your metabolic status and state of ketosis. It’s an easy calculation once you’ve taken your glucose and ketone readings: [Your Glucose Reading (mg/dl) ÷ 18] ÷ Your Ketone Reading = Your Glucose Ketone Index. But you don’t have to mess with the math because we provide you with a handy GKI calculator here. We recommend testing your GKI twice a day: after waking and before lunch or dinner as described above.

HOW OFTEN SHOULD I TEST MY KETONES AND GLUCOSE?

When you first embark on a ketogenic diet, we recommend testing often, perhaps twice a day, and also testing for food sensitivities. But generally speaking, the number of times you test each day depends on what you want to achieve. If you just want to verify that you’re in ketosis and are in a rhythm with your new diet, once a day is adequate.

If you’re turning to the ketogenic diet for therapeutic benefits around medical conditions, you may want to test before each meal to see how your day is going and, if necessary, make adjustments prior to eating to ensure you make the proper choices to maintain your desired levels of ketosis.

After several months of keto living, you should have a good sense of what you need to do to stay in ketosis, so you may not need to test as often. (Although it’s a good idea to check in with yourself periodically, as most of us tend to get a little more lax when we’re not kept in check by test results.) Several months into the lifestyle is also a good time to see if you can add more carbohydrates or protein in your diet and remain in ketosis; you’d do this by trying it out and testing your results. One of the best things about testing is that positive results encourage you to keep going. It’s fun to see the progress, especially because you can usually see it before you can feel it.

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When to Test Your Ketones & Glucose