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Monitoring your blood glucose levels in the conventional way — by pricking your fingertip with a lancet and applying the blood drop to a test strip — can be a real pain, literally, because your fingertips have more nerve endings than almost any other spot on your body. The nerve endings in your fingertips are primarily sensory receptors, which recognize pressure, pain, heat, and cold. Not only can pricking them several times a day get painful but, according to David L. Horwitz, chief medical officer of the Johnson & Johnson Diabetes Institute, “…in people who have been testing for a long time, the fingertips get sore and callused, and they can lose their sense of touch.” (Johnson & Johnson makes the OneTouch brand of blood glucose meters.)
This can be a particular hardship for people such as musicians, computer operators, and surgeons, who rely on a sense of touch for their work. But even if you don’t play the guitar or perform brain surgery, you still might want to give your fingertips a rest, says Jane Jeffrie Seley, a diabetes nurse practitioner at New York Presbyterian/Weill Cornell Hospital in New York City. Alternate-site blood glucose monitoring — which uses blood samples from areas other than your fingertips — can provide some relief.
How to start using alternate sites
To see if your current meter can be used with blood samples from alternate sites, check the package insert or user’s manual, or call the meter company’s toll-free customer service number. If you’re planning to purchase a new meter, ask your diabetes educator or pharmacist which meters can take alternate-site samples, or look up individual meters online.
Experts recommend checking with your health-care provider and/or your diabetes educator before starting to monitor using an alternative site or sites. While alternative testing sites are less sensitive to pain, getting a big enough blood sample from them can be hard to do without some guidance, which may be why few people use an alternative site instead of fingertips. “Some people like it and some people don’t,” says Seley. “They may struggle trying to get enough blood from alternative sites. They waste a lot of costly test strips and give up.”
Today’s meters, for the most part, require a much smaller blood sample than older meters, which makes alternate-site testing more feasible. “What led to success [in alternate-site testing],” says Horwitz, “is the ability to test a small volume of blood. That is why it never became popular until meters came out that could take samples of about 1 microliter or less.” If you haven’t tried alternative-site testing — or you tried previously but gave up because you couldn’t get enough blood — you might want to revisit the option with a newer meter.
Even with the smaller blood sample that newer meters require, it is still a little trickier getting enough blood to check your glucose level from an alternative site, says Dr. Andreas Stuhr, medical director of Roche Diabetes Care. (Roche Diagnostics makes the ACCU-CHEK brand of blood glucose meters.) “When you use an alternative site, you have less probability that you will hit a nerve [when you lance the skin], but you have to manipulate the site more to obtain a sufficient blood sample.”
Obtaining a sample
When to use alternate sites
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
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