Diabetics can experience frequent and strong mood swings.They could, for instance, lose their temper, lash out, become introverted or express positive emotions in a very unusual and chaotic manner. Outbursts among people who have diabetes can also become fairly common. The problem here is that they may not even be aware of these outbursts and may in fact even not remember it happening and occasionally, emotions can be expressed as melancholy, wherein a diabetic can show extreme sadness i.e suddenly cry for no apparent reason. All this can be very unpredictable, something that can often surprise and offend family members or friends. The key as family member or friend is to try and be understanding and show it too. Try not to forget that your dad doesn't mean to hurt anyone's feelings, but can't help this outburst. When he is in a good cheery mood, try to talk to him about it. :wink: