Do the blood sugar levels increase after fever?

My brother had high blood sugar levels few months back and was taking high doses of insulin along with some ayurvedic and homeopathic medicines. Gradually he reduced the insulin and ultimately left the insulin and his sugar level was normal for sometime. He is 25 years old and when his sugar was detected it was 534 and he was hospitalized for a week and he used to take 90 units of insulin per day and used to monitor the sugar levels regularly. Within a span of very few months, his sugar levels were normal and he left insulin but he is taking homeopathic and ayurvedic medicines. Now he got fever and cold after which his sugar level went up to 170 (after food) and 130 (before food). I dont understand whether this is because of fever?? He was normal for sometime. Though people say that juvenile diabetes is completely insulin dependent luckily it has not happened in his case.