Could Tiredness And Sleepiness Be Due To Diabetes?

My husband just found out that he is a diabetic the doctor prescribed him Metformin 500 gm some of the symptoms he is having is concerning me. His symptoms are weakness, sleeps all the time, which he was a very active person before he got this. He got sick with pneumonia in Febuary and got over that then has another episode of pneumonia again, since that time he has been weak. We found out about diabetes after the second round of the pneumonia. After this he has lost sense of taste, he has muscle pain in legs, back which on back he s had 3 back surgeries. He sleeps for a couple of hours then he is up the rest of the night. His hands are especially finger are like a block of ice and thumb are that way plus they are numb and swells at times. He has been light headed and when he first stands up he gets very dizzy, I told him to just stand and don t move stand a second or two before he starts to walk. he has lost 30 lbs before a months time, he was 182 now 152 that concerns me also. He had been nauseated but no vomiting. So which ever the 178 doctors can help up please I would love to hear from you. He has changed his diet, drinking alot of water, eating fish and chicken baked, some pieces of peppermint candy when he feel weak we haven t received the meter we order yet but I hope we would not have to go into that part but since he is not getting over his illness we are going to start using that and he has been eating grapes, and organges every once in awhile. I appreciated your time for your help. Thank You from Tennessee