Doxycycline interfering with insulin

My fur baby Bailey was recently diagnosed with diabetes on 5-27-14. We are rather new to this. Bailey is on 2u of Lantus Bid. I have been noticing his postperandium BG are becoming high the last few days. Slowly creeping higher. At the same time of Bailey's diabetes diagnosis he was put on doxycycline. I was reading online that doxycycline can interfere with insulin. Has anyone ever experienced any issues with doxycycline in their diabetic cats?

 

Another explanation could be his insulin needs are lowering and what you're seeing is compensatory hormones kicking in releasing stored glucose and keeping him from going too low. Some test data may help us see if that is true.

It'll help if we can see some test numbers. We have a nifty spreadsheet grid to store your test numbers in a shareable Google Drive file
Instructions are here.

Once you get your spreadsheet set up or when you look at someone else's signature link, this'll make more sense!

Understanding the spreadsheet/grid:

The colored headings at the top are the ranges of glucose values. They are color-coded to clue you in as to meaning.

Each day is 1 row. Each column stores different data for the day.

From left to right, you enter
the Date in the first column
the AMPS (morning pre-shot test) in the 2nd column
the Units given (turquoise column)

Then, there are 11 columns labeled +1 through +11
If you test at +5 (5 hours after the shot), you enter the test number in the +5 column
If you test at +7 (7 hours after the shot), you enter the test number in the +7 column
and so on.

Halfway across the page is the column for PMPS (evening pre-shot)
To the right is another turquoise column for Units given at the evening shot.

There is second set of columns labeled +1 through +11
If you snag a before bed test at +3, you enter the test number in the +3 column.

We separate day and night numbers like that because many cats go lower at night.

It is merely a grid for storing the info; no math required.