Update to an old blood-drawing method
Many people get nervous when they get poked for blood tests. Some express those nerves by clenching their fists.
Don't, if you're concerned with the test results. It could cause a spike in your potassium levels—giving a false reading for potential medical problems.
British researchers who examined 200,000 blood test results over a three- year period found that clenching and then relaxing the fist could raise potassium levels, confusing results. Many phlebotomists have been trained to administer the test in just that way. Clenching and then relaxing the hand improves flow, makes veins stand out and is effective for nervous blood- givers. More recently, training protocols have changed and asking patients to clench their fists has become an outdated practice. But old habits die hard, with some patients who often give blood samples already in the habit of clenching their fists.
Raised potassium levels can be an indicator of heart or kidney problems and could result in the over-prescribing of unnecessary drugs. Researchers found normal potassium levels upon retesting some people who had clenched in their first go-round and were found to have elevated potassium.
Best practice is that patients gently close their hand during the insertion of the needle and loosen the hand before the blood collection itself, according to the National Association of Phlebotomists.
So if you tend to be the squeamish type, just say "bloody hell," (a common British expression) unclench your fists, and submit to the needle.
