Regular self-monitoring of blood glucose levels (SMBG) gives you a quick clinical snapshot of exactly where your blood glucose levels are at any given moment. Testing, and keeping a detailed log of test results and the circumstances that surround them, will help you understand how certain foods and activities affect your blood sugar. Once you are able to detect patterns in blood glucose changes over time, you can use the information to adjust your treatment accordingly.
The Diabetes Control and Complications Trial (DCCT), a landmark clinical study, found that tight control of blood glucose levels using SMBG significantly reduced the risk of diabetes-related complications. Since the study was published in 1993, the ADA has developed guidelines on SMBG and home testing has become a recommended, routine self-care practice.
Home glucose testing is particularly important for people with hypoglycemic unawareness. These individuals have lost the ability to perceive the normal warning signs that blood sugars are dropping too low — such as shakiness, anxiety, dizziness, irritability, and rapid heartbeat.
Another role of SMBG is to help you assess how effective your medication or insulin is in controlling your glucose levels. It is also an invaluable tool for adjusting the timing of medication to ensure the best possible control.
Perhaps most importantly, SMBG can help you avoid life-threatening blood sugar emergencies. If you are under stress, sick with the flu, or taking medications that affect blood glucose levels, regular testing can help you keep close tabs on your blood sugar levels so you can take action before they go dangerously high.
Testing before, after, and possibly during exercise can help you avoid a precipitous drop in blood glucose levels. It's also wise to test if you've been drinking alcohol, another trigger for hypoglycemia. If you feel a low coming on, a quick test can confirm your levels so you can take action immediately.
I can't stand the thought of sticking myself. Can't I just test for sugar in my urine?
You could, but it would do little to help you control your diabetes. Because urine collects in your bladder for several hours before it leaves the body and only contains glucose when blood levels are over 180 mg/dl, it isn't a very timely or sensitive test. Worse, it cannot help detect potentially dangerous low blood sugar levels.