My 10 Yo Son Has Been Experiencing More Fatigue Recently.

My 10 yo son has been experiencing more fatigue recently. He is very active playing kid but he's having a hard time lately. C/o intermittent abd pain/cramping, headache at times and we have noticed decrease in concentration. He has been on vyvanse for 2 years without any increase or decreases. Treated with iron replacement for anemia for 3 months Dec-Feb and anemia resolved. We noticed he has lost about 3lbs over the last 3 weeks. Tick bite in Dec which was a female deer tick, no bullseye rash ever noted.
His paternal grandmother is a Type 1 DM, so we thought let's check him. He was 67 last night around 930 ( eaten dinner at 5 and watermelon at 8:00) Fasting this morning he was 78. Today 4 hour after eating 2 slices of pizza and 2 yogurts he is 61.

Could the vyvanse be causing reactive hypoglycemia??