ketones

Are you T1 or T2 and what control do you use? and what do you eat?
In general, you won't need to test for ketones unless you are ill. If you feel bad, do a test. A lot of ketones and high BG combined is NOT GOOD and needs a trip to A&E.

If you are on insulin, you should normally test for ketones if your BG is above about 13.8mmol, or if you have an illness. (when you're levels may go up quickly). You also need to know what to do if you have them. (ie how much insulin to take to bring down both BG levels and ketones safely) Ask your nurse for some instructions.
As Hana says high Ketones and high BS are a dangerous combination.

If its high blood glucose that has caused them, and you are able to get that sorted, lots of drinks, water, tea... will help to clear them.