Obtaining a sample
To make sure you get a large enough blood sample from an alternative site, the experts recommend these steps:
- Use the correct cap. Most lancing devices come with a clear cap for alternate-site testing so you can see the size of the blood sample.
- Wash the area to be lanced with soap and warm water.
- Rub the area briskly to warm it a bit and bring the blood to the surface of the skin.
- Hold the lancing device firmly against the skin. (Be careful to maintain contact with the skin until the blood is collected.)
- Press the button to release the lancet and pierce the skin.
- Pump three times: Loosen your pressure on the lancing device a little (without losing contact with the skin), press down again, lift, press down, lift, and press down. The lancet retracts, so you are not pricking yourself three times — you are creating a vacuum and pushing on the skin around the puncture to increase blood flow.
- Once you have pumped three times, apply the drop of blood to the test strip. (To see these steps in action, watch the video titled “Taking Your Blood Sample” at www.myfreestyle.com/freestyle-lite-instructional-videos.html.)
When to use alternate sites
You can use alternative sites if you are monitoring when your blood glucose level is likely to be stable, such as just before a meal. However, “there are certain times when alternate-site testing is not appropriate, such as when you are experiencing rapidly changing blood sugars,” says Jennifer Aspey, director of product marketing for Roche Diagnostics. There are several reasons that your blood glucose level could be changing quickly—in the following situations, you should use a fingerstick sample:
- You have just finished exercising.
- You are sick.
- You suspect your blood glucose is low.
- You have just finished eating a meal.
This is because of the way blood circulates in the body. Blood flows much faster through the capillaries in the fingertips than through other parts of the body, which means blood samples drawn from them reflect changes in glucose level faster. A blood glucose reading from an alternate site, on the other hand, can have a lag time of up to 20 minutes. Different concentrations of muscle, fat, and blood vessels in different areas of the body can also affect blood glucose levels.
This does not mean that an alternative site is giving you a wrong value, Stuhr says. It is as accurate as a value from a fingerstick sample — if you are fasting or in another stable glucose state. If you check your blood glucose using an alternate-site sample right before or two hours after eating, you should get a reading that is similar to a fingerstick sample.
Seley tells her patients to use alternate-site testing before meals but to use the finger or palm after meals. “It’s hard to know when the rise in blood sugar is after a meal since it depends on the amount of fat eaten, which can delay the postmeal rise in glucose. I would rather my patients be safe than sorry.”
Experts say that you should not try to correct for the difference, or guess what your blood glucose level really is. If the value seems off or doesn’t match how you feel at that moment, check it again. “Whenever you get a value that doesn’t match how you feel, you should always repeat it, regardless of where the sample came from, and if you repeat it, I would repeat it using the finger,” Seley says.
Giving your fingers a break
If fingertip pain or callusing is getting in the way of regular blood glucose monitoring — or just causing you more discomfort than you care to live with — consider giving alternate-site monitoring a try. You may need to spend a little time learning a new lancing technique, and you’ll need to remember some guidelines for when and when not to use alternative sites, but the payoff can be fingers that look and feel better and possibly a greater willingness on your part to monitor more often since it hurts so much less.