Tips for when to test for consistency.
1. Test before you break your fast to get a good baseline of what is in your blood. For glucose, you want to wait a couple hours after waking due to the "dawn phenomenon" which can cause you to have a higher fasting glucose reading than you otherwise would.
2. Test at a similar time each day if you can to keep the results more consistent.
3. If you test after eating specific foods, test at a similar time interval. For example: 40, 80 or 120 minutes after the meal. This is primarily for glucose as ketone levels will rarely be affected that soon after eating.
4. Keep in mind that rarely will something you ate today affect your ketone readings the same day. Usually it takes a day or so for that to register. It's different for glucose readings, those will spike within 30-90 minutes usually. The exception to the ketone readings would be exogenous ketones, those can affect ketone readings within 30-90 minutes.
5. Remember that exercise also can affect your measurable ketone levels.
6. Keep in mind, with ketones, bigger numbers are not always better. A reading of 4 or 5 isn't better than a reading of 1 or 2. A high reading could mean that your body is very good at producing ketones, but possibly your body isn't great at using them yet. Usually once you are fat adapted, you will rarely see those high numbers but you are doing great!
Everyone is different, if you are in the zone, you are doing well.