Hi Carlos,
The recommended test times are usually before a meal, then 1 hour after, then 2 hours after. The theory is that:
- the before test gives you your benchmark to compare the other tests against
- at 1 hour the food you have eaten will have pushed your BS to about it's highest level
- at 2 hours your BS will be showing a distinct drop back toward the start point.
If you want to do a further test then at 3 hours you should be back to where you started.
That's the theory, and it is a good general guide, but it's only an approximation and can be thrown out by several things. If the carbs in your meal were mostly high GI then your BS will have peaked in much less than an hour, if they were very low GI they could still be being converted into glucose 2 hours after eating. Fat also slows down the rate of conversion into glucose and absorbtion into the blood stream, so a meal containing a high fat content can make even a high GI food act more like a low GI food.
This is why you can sometimes get unexpected results from the tests - after a lowish 1 hour test you might think "that food didn't have as bad an effect as I thought it might" - but that could be simply because it hasn't finished converting into sugar after 1 hour. Similarly you could be surprised at a high 2 hour test, when what you are seeing is something that has only just peaked at 2 hours.