It's one of the first things newly diagnosed diabetics are advised to do before they test their blood glucose: wash your hands. But when soap and water are not available, some experts recommend another strategy: place the "second drop" of blood rather than the first on the test strip.

A new study is suggesting that using this second drop after wiping away the first drop may be an acceptable alternative to handwashing.  

The study appeared in the journal Diabetes Care. It was conducted by Dutch researchers and focused on 123 individuals. They tested their blood sugar under several conditions:

  • after they washed and dried their hands
  • without washing their hands
  • after handling fruit (known to leave a sugary residue on the fingers)
  • after they washed their fruity fingers

For the study, the subjects tested their blood sugar employing a variety of amounts of pressure to obtain the blood. (Many guidelines specify not to squeeze the finger to get blood as it may change the blood sugar levels. Typically, the readings are lower when people put pressure on the finger.)

"Ideally, your hands are clean and dry, you prick your finger, and you measure with a blood glucose meter," says Ronald Tamler, MD, Ph.D, of Mount Sinai Medical Center in New York City. "But you may not always be able to wash your hands. The researchers found that clean hands are still key, but a second drop is a good idea if there is no way to clean your hands."

Another alternative to handwashing is to use a hand sanitizer, but some alcohols may interfere with the test strips.

So is the using the "second drop" as good as handwashing?

When the researchers examined their test results, they found that compared with tests of clean hands:

  • Some 11 percent of the people in the study had test results that were at least 10 percent inaccurate when they went with the first drop after not washing their hands.
  • Some 4 percent of participants who hadn't washed their hands and who used the second drop of blood had test results that were at least 10 percent off.  

Not washing the hands isn't the only practice that can give inaccurate blood glucose readings. Handling sugary foods before testing (and not washing the hands) is another.

Tamler learned firsthand of how sugary hands can skew a blood sugar reading. One of his patients was a mom who was in good control and whose blood sugars began to be out of whack. When he looked into the matter, he found that she had been baking each week with her kids, handling starches and sugars. Her blood sugar was always very high after coming into contact with the baking ingredients even though she hadn't actually eaten the baked goods.

"Her blood glucose levels miraculously normalized after meticulous hand-washing," Tamler wrote in an article. "I guess this give a new meaning to saying to a patient, "You have a touch of sugar!"

Hortensius, Johanna, and others. "Self Monitoring of Blood Glucose: The use of the first or the second drop of blood."  March 2011. Diabetes Care.

Tamler, Ronald, MD, Ph.D. "A Touch of Sugar." 1 July 2009. Endocrine Today.

" 'Second drop' sometimes OK for blood sugar testing." 8 March 2011. Reuters Health.