The common and early symptoms of diabetes result from the effect of the high blood sugar entering the urine and drawing fluid from the body’s tissues along with it. This leads to excess urine production with frequent urination. The loss of body fluid leads to thirst, in order to replace the fluid loss. As long as the person with diabetes is able to keep pace with his or her thirst by regular fluid intake, he or she will remain relatively well.
However, without free access to fluid, which can occur for a variety of reasons, one will become dehydrated, which leads to dizziness upon standing upright drowsiness, confusion, and ultimately fainting and unconsciousness. Due to the wasting of calories as glucose in the urine, patients will complain of hunger and will usually lose weight if high blood sugar is very marked. However, it is important to note that only a minority of people with diabetes will experience these symptoms.
Frequently, the degree of high blood sugar is more moderate, with little sugar entering the urine and causing no immediate symptoms. However, diabetes of even modest severity can cause considerable harm and lead to serious chronic complications. Therefore, it is important to detect diabetes that is asymptomatic (i.e., without symptoms), which is the reason that screening programs to detect diabetes in those at highest risk have been developed.
If asymptomatic diabetes is not discovered for a sufficiently long period (many months or years), patients may actually present with long-term complications of the previously unrecognized diabetes, such as heart attack, stroke, heart failure, neuropathy (nerve damage), nephropathy (kidney damage), or retinopathy (eye damage).