By 
Diabetes mellitus occurs when you have a problem with the pancreas, which is the organ that controls blood glucose. Either it stops making insulin or it doesn’t make enough insulin to meet your body’s needs. This insulin deficiency results in impaired absorption of glucose by your body’s cells, which use it for energy, as well as by your liver, which stores it. The end result of this malabsorption is high blood sugar, or glucose.
There are two main forms of diabetes mellitus. They are type I diabetes (also called juvenile-onset or insulin-dependent) and type II diabetes (also known as maturity-onset or insulin-independent).
In type I diabetes (insulin dependent); which usually affects young people, the pancreas produces little or no insulin. The defect is caused by damage to insulin-producing cells. Your body, unable to use glucose due to lack of insulin, is forced to obtain energy from fat. This can lead to a dangerous condition called a diabetic coma.
In type II diabetes (insulin-independent); that commonly strikes people in their forties, the cells that produce insulin are still working, but the amount of insulin is insufficient for your body’s needs. Patients with this type of disorder often eat too much and are overweight. Overeating causes excess glucose in the blood and the pancreas cannot produce enough insulin to cope. Genetics and hereditary factors are key players in this type. In a third of cases, there is always a relative or relatives who suffer from the disorder. Another factor is your age, because the function of your pancreas declines as part of the normal aging process.
All forms of diabetes cause the same main symptoms. You urinate a lot more than usual, sometimes every hour or so, throughout the day and night. You may notice white spots, which are dry splashes of glucose-filled urine, on your underwear or shoes. Microorganisms are attracted to sugary urine and these can cause various complications such as bladder infections. Excessive fluid loss can cause you to be perpetually thirsty, and drinking sugary drinks increases the amount of urine you urinate and makes your thirst worse. Your cells don’t get enough glucose, so you feel extremely tired, weak, and listless; so much so that you may not be able to get up in the morning.
If you are diabetic or a parent of a diabetic child, you may notice excessive weight loss. This is explained by the body’s inability to use glucose as an energy source, and instead your body begins to burn fat and muscle. Other symptoms you may experience include tingling in the hands and feet, decreased immunity (small abscesses and burning when urinating due to infection can be early symptoms of diabetes), blurred vision due to excess glucose in the fluid in the eye and loss of erection in men or the absence of menstruation in women.
The symptoms of type I (insulin dependent) diabetes usually develop quickly, over weeks or months. Those of the Type II (insulin-independent) form often do not appear until many years after the actual onset of the disease. Sometimes the disorder is discovered by chance during a routine medical exam, before symptoms appear.