Although hypoglycemia is possible after gastric bypass, in most cases low blood sugars can be controlled with diet. In rare cases hypoglycemia can be severe. I, unfortunately, developed severe post-operative hypoglycemia three years after having gastric bypass surgery. 

I struggled for years to discover the cause behind my severe drops in blood sugar, which didn't seem to be responsive to changes in my diet, and over time it got worse. However, I have had some success by going on thyroid medication. 

I have a history of nodules on my thyroid, but was taken off my thyroid medication about a year after weight-loss surgery. My thyroid numbers were in the normal range, (but on the low side). After doing some research I suspected I was suffering from multiple thyroid symptoms. I was put on Armour Thyroid medication—my blood sugars are more stable and I am able to exercise with no any symptoms of low blood sugar.   

If you have worsening symptoms of low blood sugar with no help from diet and or have exercise induced hypoglycemia, you might consider consulting a doctor. You may need medication to regulate your insulin levels. It also may be a good idea to get your thyroid checked.