Checking your blood sugar at home is Okay, but you cannot depend 100% on it. When you try the same in a lab, you will get a different reading. This is because, when you are trying at home for example you just take blood from your index or middle finger, the blood is not an actual blood what you get. It contains more sugar as you get more fluid from peripheral side. So obviously, the reading will be higher sometimes. That's why lab technicians draw blood from veins some deep into the skin and not from a finger.