Hi payal3,
As it is reactive hypoglycaemia, your father SHOULD have been advised on how to control this.
Your father should eat 5 or 6 smaller meals per day, rather than the regular 3 times a day.
His diet should consist of eating fewer carbohydrates, but should also include a higher proportion of fats and/or proteins.
In reactive hypoglycaemia, what occurs is that the pancreas 'over-produces' insulin in response to the foods and drinks imbibed, which is what's causing him to lose consciousness.
Carbohydrates are broken down to release glucose, which is abosrbed through the walls of the intestines into the bloodstream. Fats and proteins slow down this absorption.
In theory, if there isn't such a quick rise in blood glucose levels, the pancreas wouldn't need to produce so much insulin to deal with the rise.
I don't know whether you live in the UK, my friend, but most packaged foods and/or drinks do contain a list of their contents on the wrapper. If your father eats more fresh foods, I'm afraid you'll need to do a bit of research on the carbohydrate content of the foods/drinks.
You could also ask your father's doctor to refer you to speak with a dietitian as s/he would be able to offer better advice on this than your father's doctor would be able to.
Sadly, there is no 'magic pill' that will 'cure' anyone of reactive hypoglycaemia.
I wish you well, and truly do hope that your father is able to get a better grip on his condition.
Lots of Love and Light.
Mick
x x x x
x x x
P.S. Please don't be offended, or alarmed, at the 'x's'. It's merely a logo, of sorts, that I've used for more than 40 years now.