My husband is 52 yrs, controls his diabetes with strict diet and exercise. Has low insulin production but is in the low -normal range. My husband has some depression factors, agitation, and explosiveness since becoming diabetic. If your husband is controlling his blood sugar with his program I would urge him to continue it.
Many people become angry, frustrated, depressed etc. when they are diagnosed with diabetes.
This is not a direct result of high blood sugars, but rather having to adjust to the realization they have a change in their health. If this is interfering with his management of his diabetes or his daily activities I would talk this over with his health care provider or seek out the advice of a mental health provider who has experience with people with diabetes. It is also important to realize that the emotional issues may be unrelated to the diabetes. This may be due to insufficient food intake, increased exercise, variable absorption of the insulin from the injection site, timing of food intake and insulin injection etc. As a result no herb or vitamin will correct these problems which are often infrequent and unpredictable.