What if you could keep close tabs on your blood sugar without losing a drop of blood? Under-the-skin sensors that monitor glucose levels around the clock and sound an alarm if levels get dangerously high or low are increasingly available to people with type 1 or type 2 diabetes. This article from our Health After 50 newsletter explains the benefits of the continuous glucose monitor.

If you have diabetes, you know that you can't eat just anything or take a longer walk than usual without being prepared, especially if you require insulin injections. Food and exercise both change blood glucose levels, as do stress and illness. Sometimes, you might need a snack to stop levels from falling or a dose of insulin to head off a spike in blood sugar.

Consistently high blood sugar leads to diabetes-related complications like vision and kidney problems; dramatic drops in glucose levels (hypoglycemia) can cause dizziness, anxiety, and confusion. In severe instances fainting or brain damage can occur. Monitoring your blood glucose levels lets you know if your medications are working and alerts you to potential problems.

The old way. The most common glucose measurement is hemoglobin A1c. Hemoglobin is a protein in red blood cells with glucose attached to it. Three or four times a year, your doctor tests your blood to see if your A1c levels are higher than normal. A1c is a helpful measurement of your overall control of blood glucose, but it can't give the information you need to make day-to-day decisions.

Home blood tests provide a closer look at glucose levels. Traditional self-monitoring means pricking your finger to get a drop of blood that you then apply to a test strip. A handheld glucose monitor reads the test strip. This process may be repeated several times a day to provide snapshots of your glucose control.

The new way. Newly available continuous glucose monitors allow you to follow your glucose levels 24 hours a day. Every three days or once a week, depending on the type of monitor, you inject a tiny sensor under the skin of your abdomen. A transmitter that is attached to your skin by an adhesive patch picks up glucose readings from the sensor and sends them to a small monitor that is worn on your belt or waistband.

Constant monitoring allows you to see what your glucose levels are and if they are headed up or down. Changes that require action (a snack or insulin dose) should be checked against a conventional finger-stick test -- so using a continuous glucose monitor doesn't mean you're free from finger pricks. Continuous glucose monitors are fairly accurate but not as reliable as traditional glucose tests.

The cost of convenience. It takes time to learn when and how to act on readings that are coming every 1 to 5 minutes. You might test your blood sugar four times a day with a conventional monitor; a continuous glucose monitor will give you hundreds of readings. It's important not to overreact to changes.

Continuous glucose monitors are expensive and may not be covered by insurance. The monitors cost up to $1,000, and supplies can cost as much as $350 a month. Different models vary in size and in how often they provide readings. Accuracy among the different models varies slightly, but these variations shouldn't matter as long as you calibrate the continuous monitor with conventional finger-stick tests.

Bottom line: The greatest benefit of continuous glucose monitoring is that it gives you and your doctor a more complete picture of how well you are controlling your blood sugar. For instance, a continuous sensor is the only way to know if your glucose levels drop overnight. The continuous glucose monitors can help you spot general trends, recognize whether your blood glucose is on its way up or down. Better yet, the new sensors even include alarms that can warn you if your blood glucose is too low or too high.

Continuous glucose monitors require commitment and training to be used effectively. You must be willing to make dietary decisions and treatment changes based on the information you receive. Eventually, however, you may find that keeping closer tabs on your blood sugar means you have less -- not more -- to worry about.