What’s the Best Time to Test Blood Ketones?

In a Nutshell: The best time to test blood ketones is before main meals, particularly for those following intermittent fasting, to get the most stable readings. Avoid testing first thing in the morning, immediately after meals, or post-exercise to prevent misleading results.


  • Optimal ketone testing requires timing; test before main meals, especially for those practicing intermittent fasting, to avoid the fluctuating levels influenced by the Dawn Effect or recent food intake.
  • The testing frequency should be balanced; twice daily offers a stable insight into ketone levels without the redundancy of over-testing.
  • Testing immediately post-exercise can lead to misleadingly low ketone readings, as physical activity increases the body’s utilization of ketones for energy.

Decoding the Best Time for Ketone Testing

The pursuit of optimal health often leads us down the path of meticulous self-monitoring – a journey where precision is vital. This rings especially true in the realm of ketosis, a state coveted by many in the low-carb community. 

Dr. Dan Maggs, a Locum General Practitioner and a beacon in the low-carb world, sheds light on a crucial aspect of this journey: the best time to test blood ketones.

The Art and Science of Ketone Testing

Dr. Maggs, who transformed his health and weight through low-carb nutrition, emphasizes the importance of testing and testing right. “Blood ketone strips are expensive,” he reminds us, “and we don’t want to be wasting them.” 

He outlines several times during the day when testing might lead to misleading readings.

Morning Tests and the Dawn Effect: Testing first thing in the morning? Think again. Dr. Maggs points to the ‘Dawn Effect’—a surge in hormones like cortisol and adrenaline in the early hours that leads to a spike in blood glucose and a dip in ketone levels. His advice? Wait at least an hour after waking up to test.

Post-Meal Readings: Just had a meal? Hold off on that ketone test. Even low-carb meals can cause a temporary drop in ketone levels due to insulin release.

Post-Exercise Numbers: Exercise, while beneficial, can also temporarily lower ketone levels as the body uses them for energy.

The Ideal Times for Testing

So when is the best time to test? Dr. Maggs offers a clear strategy. “The best time of day to test is before your main meals,” he says, suggesting times like 12:00 PM and 7:00 PM, especially for those following a 16:8 intermittent fasting pattern.

How often should one test? Dr. Maggs advocates a balanced approach: “Twice a day will give you a good idea if things are stable.” 

He warns against over-testing, noting that adding a third testing point doesn’t significantly enhance understanding of one’s ketone levels.

The best time for testing can vary from person to person. Dr. Maggs encourages finding a pattern that fits one’s lifestyle and sticking to it while avoiding the common pitfalls he outlines.

Effective Ketone Testing

By understanding the physiological processes at play and testing at optimal times, individuals can gain accurate insights into their state of ketosis. According to Dr. Maggs, this is crucial for anyone on a journey toward sustainable weight loss and improved health through a low-carb diet.

As the keto community continues to grow, voices like Dr. Maggs’ are vital in guiding enthusiasts toward achieving ketosis and understanding and optimizing it. With his blend of personal experience and medical expertise, Dr. Dan Maggs continues illuminating the path for many in their quest for healthful living.

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