Checking Your Blood Glucose 101

The first time is the hardest.

Having to prick your own finger—actually drawing your own blood, intentionally—is a clear sign that your life has suddenly changed.

But being able to check your blood glucose whenever you need to is in fact an extraordinary accomplishment of modern medical science, and one of the most important tools for fighting diabetes, so the sooner you get comfortable with it, the better. That little ouch will help make you an expert at managing your condition and give you a start on staying healthy for life.

Why Glucose?

Glucose is a type of sugar and the body’s main source of energy. The carbohydrates in the food you eat are broken down into glucose, which then travels around in the blood to nourish your cells. But diabetes causes problems with the body’s use of glucose, trapping it in the blood where it can do damage over time, particularly to the eyes, kidneys, and nerves.

In type 1 diabetes, this happens because the body can’t make its own insulin anymore and it needs the insulin to process the glucose. In type 2 diabetes and gestational diabetes (the kind women develop in pregnancy), there is still some insulin, but the body isn’t using it well enough and, again, can’t get the glucose where it needs to go.

Blood glucose levels that run higher than normal can cause serious long-term complications and are the reason that people with poorly controlled diabetes can go blind, lose their kidney function, or have foot or leg amputations.

Luckily, it’s been shown that keeping glucose under control helps people with diabetes prevent these debilitating and sometimes deadly complications. The American Diabetes Association recommends that most people with diabetes aim for an estimated average glucose (eAG) of less than 154 mg/dl, as measured by the A1C test. (The A1C test is an estimate of a person’s average blood glucose over the past three months, and an eAG of less than 154 corresponds to an A1C of under 7 percent.)

That said, it’s important to recognize that everyone is different, and your doctor may set a different target for your A1C or eAG depending on your age, how long you’ve had diabetes, and other factors.

You may have specific goals for your glucose levels when you wake (“fasting” glucose), before meals, and after meals (“post-prandial” glucose), too. And you’ll also get some guidance on what to do if your glucose is too low—a condition known as hypoglycemia, usually defined as a blood glucose level below 70 mg/dl. Hypoglycemia can cause impaired judgment, erratic behavior, and loss of consciousness; it can even be life threatening.

High, Low, High, Low

Figuring out what makes your blood glucose move up or down is key for figuring out how to get it under control. In brief, eating, stress, and illness can make glucose levels rise, while medication and exercise tend to bring them back down.

But there’s a certain amount of trial and error in learning how your body reacts to every one of these factors—and that’s where proper glucose monitoring can make a huge difference.

Testing and measuring

To test your blood glucose, you’ll need a meter: a handheld electronic device that can determine how much glucose is in a blood sample you provide. There are many varieties on the market, so you should consult your physician or diabetes educator to learn more about meters’ different features.

You’ll also want to find out whether your insurance will only pay for certain models. In addition, you’ll be given prescriptions for lancets (or similar devices) to pierce your skin and test strips that are used to channel the drop of blood into the meter.

Measuring blood glucose; image source:

How often you check your blood glucose depends on what you use the results for. If you are using your measurements to guide insulin use, your doc may tell you to test every time you eat or take insulin—three times a day, or more.

How often should blood glucose be measured?

You will probably also want to check blood glucose before and after exercise or any other time you think you may have a low. (People prone to hypoglycemia should check every time they get behind the wheel of a car, for example, just in case.) Those striving to keep their glucose levels as close to normal as possible (say, during pregnancy) may wish to check even more often.

If you are on only oral medications, have type 2 diabetes, and have good blood glucose control, your doctor may tell you to check your levels less frequently. Some people on oral agents or no medications for diabetes can do well without testing at all. In any case, you will want to determine beforehand how many test strips your insurance company will pay for, or how many you can afford yourself.

Bring your results when you visit your provider. Later, if you and your health care provider decide you need more information, you may consider switching to a continuous glucose monitoring (CGM) system.

These devices take glucose measurements every few minutes through a disposable sensor placed just under the skin. CGMs give a detailed look at glucose levels throughout the day and night. Alarms can be set to warn of glucose highs and lows, although CGM users must still monitor their blood glucose to calibrate the device.

Yes, there’s a lot of information to be found in that little drop of blood. Working with your health care providers, you can use it to make good choices that will have lasting results.


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