Blood sugar raised....virus?

Hi, I was diagnosed with type 2 last year and am taking metformin, which seemed to be working. However last night I was up all night with vomiting and an upset stomach...at one point I felt as I was going to pass out, spoke to nhs direct who asked me to check my sugar level which was 12.9 and was advised to check throughout today ...the highest has been 13.5 keep going hot and cold so am pretty sure have picked up a virus. Would this be the cause of the raised levels?
Thanks

Checked again this morning and was down to 11.1 and this evening is back to 13.1. How high is too high? and how long should it be before its back to normal(I'm feeling much better today but still not 100%
Thanks for your reply...it's much appreciated, I still havn't really got to grips with everything!

Hi,
Thanks again for your reply...I don't have the strips to check for ketones, my levels today have been between 11 and 13 again, to be honest the first blood test i had after starting metformin were so good that the nurse basically said just keep on doing what you are doing! I'm just concerned that maybe the readings should have gone back dowm now as it was wed night/thurs morning that I was ill, and although up until today wasn't feeling great I have had no more upset stomach or vomitting. Is it usual to still have raised bg after 2 or 3 days.(Sorry these probably sound like small concerns to some who are so much worse, but after reading these forums I realise I know nothing!!) :?