Funny that you ask, I just got thru woofing down a huge chunk of lemon meringue pie. Yum-yum. My backyard has both Meyer and hybrid grafted Eureka/Lisbon lemon trees so I consume them on a regular basis in a variety of ways.
Lemons do not lower glucose levels. Lemon juice when added to other foods lowers the glycemic index of those foods. This often is misconstrued as lemons lowering glucose levels. With lemon juice, t2 diabetics can digest food easier without risking elevated glucose levels or putting their glucose levels at risk. So go ahead and enjoy those lemons.
Lemon's may not do the trick but if you eat something that you think is going to make your blood sugar go up drink lots of water right after eating and it will equalize it self out i now this becuz when i was preg. with my daughter i had ges. diebetes. had to check my blood sugar 4 times a day.