What if any affect radiation for a brain tumor might have on bs levels

@ddbrown61 Welcome to Mayo Connect, I hope your treatment so far is going well. That is a very important question, one many people would not know to ask!

Radiation, by itself, should have little impact on your blood sugar. However, steroids are often used to reduce swelling in the brain during radiation, and can cause elevated blood sugar, which can start suddenly and without warning.
This is even more probable if you already have Type I or Type II diabetes, and are on insulin or medications.
So, prior to the star of radiation, your blood glucose and A1C should be checked. And you blood sugar should be monitored. The best way is for you to test it yourself daily with a glucometer, but if that is overwhelming with everything else going on, it should be checked before every radiation treatment, and with every doctor or nurse visit.
We did not know this when my mother-in-law was having radiation for a tumor, she had no history of diabetes or pre-diabetes, and we didn't realize what was going on until she had ketosis. It was at that point when the hospitalist told us what the radiology clinic should have been doing.
Sue

Thank you for a quick reply.
I have type 1 and am insulin dependent. I am also using a cgm I imagine wtching my cgm frquently will be helpful and paying attend to my alerts will also be very important,

@ddbrown61 I want to add my welcome to you also. @sueinmn had some great great comments regarding your situation. In addition to what Sue said I want to remind you that Diabetes affects everything else you might have and vice versa. I’m diabetic too, going on 50 years. I also have a continual glucose monitor (CGM) and an insulin pump. I recently had an MRI as a routine follow up for a lesion identified a year ago during a CT scan. I don’t have a lot of experience with radiation but I think scans of any kind involve some radiation. In addition to removing all metal (jewelry etc.) I had to remove the CGM sensor/transmitter, the insulin pump and my hearing aids so that the electronics wouldn’t be screwed up! Before you start these radiation treatments you should be given the chance to hear about benefits, risks, alternatives…. Blah, blah, blah and the opportunity to ask questions. Maybe you can ask about the impact it may have on your blood sugar and what to be aware of regarding your CGM? Knowledge is powerful as is preparedness!