Even a 1 per cent rise in blood sugar levels over the month can lead to a 20 per cent increase in the likelihood of developing diseases that affect the heart, kidneys and nervous system.
Doctor sees blood sugar rise at end of the fast
Towards the end of Ramadan, a worrying trend emerges among Dr Mazen Askheta's diabetic patients.
"My chronic patients come to me after the month of Ramadan and their diabetes control has gone tremendously wrong because they haven't been eating properly," Dr Askheta said.
"They shouldn't be fasting but they fast, and they over-eat after sunset so their diabetes is really very much out of order."
Other endocrinologists see similar behaviour patterns and similar problems.
"I think it's a mixed bag," said Dr Hamed Farooqi, the director of the Dubai Diabetes Centre.
"It's not that everyone has high sugar but generally what we do see is that people are not that particular about their diet during Ramadan, so we do see some elevation."
Diabetics should be moderate in their eating, Dr Farooqi said.
"It's a fairly long fast these days, but that doesn't mean you should eat everything that you can get down," he said. "The local customs are that people just keep on eating until two or four in the morning and don't think about it."
Even a 1 per cent rise in blood sugar levels over the month can lead to a 20 per cent increase in the likelihood of developing diseases that affect the heart, kidneys and nervous system, said Dr Askheta.
"We try to remedy the damage that unfortunately many of them do," he said.
"There are just a few patients who do better during Ramadan because they have been trying to adhere to a much healthier plan."
Reversing the effects can take weeks, even months.
"Unfortunately, many don't exercise during Ramadan and many of them indulge in these iftar buffets, so it takes us two or three months to get them back to the base line," Dr Askheta said.
"We do this by either changing their insulin regimen or changing their medication, and we try to emphasise going back to a healthy diet and exercise plan."