That is not a stupid question.
For me it was a couple of issues. When stomach empty and no more glucose from digestion, BG would slowly keep drifting up instead of stabalizing and stopping and then slowly drop.
Another clue is that peaks on digestion will be much higher than food eaten would warrent.
Third would be the appearance of dawn phen that has high levels like greater than what it was at midnight. 110 at midnight 150 at 3:00 am and much higher at 6thru 8 am. Mine was reliably 238 at wakeup.
Some may point out that the liver is signalling poorly on available insulin and dumping in excess glucose. The liver works on the inverse of the insulin level; the lower the insulin; the higher the glucose that will be added by liver on a liver function. Some folks on pumps and needles may be able to add basil insulin doses and if liver signalling working properly, the basil insulin may correct dawn phen.
When blood glucose drops sub 70; liver is supposed to add glucose to bring up the bloodg lucose to 20 percent above nominal max. Any higher than an issue. Unfortunately, the liver signalling can be faulty or the insulin levels extremely low and or all of that plus leaking.
In the case of faulty signalling, metformin will cut off excess liver glucosea add.
In my body, when blood glucose drops sub 70, the liver would throw the whole liver buffer at the problem and I would see my blood glucose shoot up to 511-max on caveman machine and then slide back to 278-311 as heart pumped stuff around the body averaging out the readings.
Because my liver would throw the whole buffer at the problem; I called that a dump.
For me, metformin solved the problem as well as the dawn phen.
Another flag may be a1c that will be higher than expected assuming proper diet, clories input and sufficient exercise. Here most folks unless on cgme are not watching BG during sleeping hours to see what is happening. During the conflagartion, my a1c was 13.3.
as pointed out by Brian (bsc), one really needs to check into diet/ food, calories, exercise as well as insulin used to be sure one is not missing anything as well and inadvertantly spiking the ball.