There are three main reasons why you may be in ketosis before going to sleep but not in ketosis when you wake up.
Taking exogenous ketones
One of the most common reasons for being in ketosis at night, but not being in ketosis in the morning is the use of exogenous ketone salts during the day. The fact of the matter is that exogenous ketones, although they MAY be useful in some situations (see “Should I take exogenous ketones?”), most of the time, exogenous ketones only make you APPEAR to be in ketosis.
They affect both urine and blood ketone testing by making the tests positive, despite research showing they are not ketogenic and do not help your body reach or maintain ketosis. In fact, research shows that they inhibit ketogenesis (the creation of ketones by the liver) which is the whole point of ketogenic diets (for non-medical reasons).
Basically, if your body has enough ketones for its fuel requirements by taking exogenous ketones, it has no reason to break down body fat for fuel. You may appear to be in ketosis when you go to sleep, but as the pills wear off, your true ketosis status in the morning is tested. Exogenous ketones ultimately give you a false sense of security by making you think you are in ketosis when your body really isn’t.
Late-night eating can also cause you to be in ketosis at night, but not in the morning. Typically, this happens when you eat carbs late in the day and then go to sleep.
As your body’s metabolism slows down while sleeping, the carbs are not burned as quickly and they kick you out of ketosis. Something that doesn’t kick you out of ketosis when eaten for lunch, may not have the same effect if you eat it as a midnight snack.
All of this is assuming your carb intake doesn’t increase before going to bed. If you do eat more carbs at night than during the day, it can wreak havoc on your ketosis.
Checking ketones at the wrong time
Similar to the previous reason, checking ketones after you eat, but before the food has a chance to digest can give you a false positive as well. You will test positive for ketones, but once the food is digested and the carbohydrates enter your system, they kick you out of ketosis while you are sleeping.
This can be even worse with urine testing than blood testing due to the fact that blood tests are real-time indicators of ketosis status and urine testing indicates ketosis status from a while before.
Personally, my blood glucose rises (and ketones drop) starting around two hours after eating carbs. If I eat something at 9 PM and then test myself at 10:30 before going to sleep, I may still get positive testing results on my blood ketone test and yet, an hour later, be out of ketosis. There is even a greater lag for urine testing.
Using the same scenario, if I ate carbs at 9 PM, I would still be out of ketosis by 11:00 (same as before), but then it takes time for the ketone levels to drop in the urine. It may be hours before the average level of ketones in the bladder drop enough to even show you are out of ketosis.
See: “Should I use a ketone meter instead of urine test strips?” for a discussion about ketone test timing and accuracy. You may very well still show that you are in ketosis at midnight (in this case), even though you got kicked out from the 9 PM meal.
If you find yourself not in ketosis in the morning despite being in ketosis before going to sleep, these are the primary things to consider. Unless there is a good reason you are taking exogenous ketones, don’t use them (see the appropriate reasons to use them in “Should I take exogenous ketones?“).
They will give you a false sense of security. As for the last two reasons, be mindful about what you eat before bed as well as when you eat and when you test.
You will also need to take what type of testing you do into consideration. The best recommendation is to not eat late and use a blood ketone test meter instead of urine strips until you can identify which of these issues you have.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.