so, the way i think of it is like this: every different type of tissue in your body needs a different amount of insulin to function – your kidneys need some, your muscles need some, your fat needs some, your liver needs some.
Normally, the amount of insulin you need to keep your blood sugar steady exactly lines up with the amount that each of these tissues need to function properly. BUT when you are exercising, your muscle is able to take in more sugar from the blood with less insulin. That, however, doesn’t mean your kidneys or your fat or your liver need any less insulin – they may even wind up needing more. So there can be this weird mismatch – your muscles are helping keep your blood sugar steady and level, but meanwhile your kidney or liver tissue could be cranking out ketones to compensate for what it perceives as a lack of insulin.
With our son we’ve seen that he can develop HIGH ketones even with perfectly normal blood sugar over night – sticking close to 100 – when his pump was accidentally suspended. He was in the mountains at altitude, so what we think happened is that his muscles and his heart, etc. needed more blood sugar to function, but all the other organs still need some insulin, so he developed high ketones.
In fact, just last night dad forgot to plug his pump back into his site after bath time and he woke up with a blood sugar around 200. That’s for sure high but it’s technically “in range” for him, and he was basically steady at that number or lower all night. But his blood ketone meter read 3.2, which is high. I reconnected and gave him his breakfast bolus without thinking, and then set a high temp basal. He actually went LOW after that but when I tested his ketones an hour and a half later, they were still 1.4, which is still high.
Anyways, all that is a long-winded way of saying that if you check your ketones you will have reassurance that you’re not developing ketones. Even if you are it’s something that can be managed of course. I don’t think the answer to exercise is “swim at 200.”