I haven't had a glucose tolerance test but I have had an insulin stress test where I was starved then had a huge dose of glucose administered to see how my body managed this situation...and it made me feel lousy, and yes I felt exhausted afterwards. Hyperglycemia can cause sleepiness, in a non clinical setting it needs medical advice but because this was induced I wouldn't say it was a problem. The tiredness is caused because your body is working extra hard to use up or rid your body of the excess glucose. Usually you feel the "sugar rush" when you have a rapid intake of sugar, this means your body's workload has temporarily increased. Being pregnant in itself is tiring but this extra work is an added strain.

I only did the test with my first, never did it with my second. Being sleepy could have been from sitting around waiting for them to take your blood after an hour (assuming you sat around). It did make me feel sick when I took it, that is a normal side effect from it.

I didn't get really sleepy but I did feel really sick.

I was both really sleep and got sick. My doctor explained this can be a usual sideeffect as your body tries to process all of that sugar.

No I never got sleepy from it but I did get nauseous after I drank it. It most likely was because it was too sweet since it's basically sugar water. I'm not sure why it would have made you so tired. I would suggest talking to your OB doctor to see if it could possibly have been a side effect from the glucose drink or if it was normal.

Anytime you eat a large meal consisting of lots of carbs, you may feel sleepy (the way you might feel after Thanksgiving dinner.) I could not find specific information about this being related to a glucose tolerance test, but it is not surprising that it would occur after drinking large amounts of sugar. Nausea is also a common result of having to drink the solution, and would be even more likely to occur when you are pregnant.