I have first hand experience this ,as I was recently diagnosed with reactive hypoglycaemia[1]. The recommended treatment was eating protein and vegetables before carbohydrates, along with daily 12 hour fasting, and within week my symptoms were gone. It's apparently an intestinal issue, where it over-reacts to the presence of carbs when the stomach is empty, and is fairly common in people who have had bariatric surgery.

[1] https://en.wikipedia.org/wiki/Reactive_hypoglycemia