08/16/2011 02:17 pm ET | Updated Oct 16, 2011

Should We Think Twice Before Drawing Blood?

When you're sick, the gap that has opened up between you and better health presents many mysteries to a doctor. What's wrong with you? How much of a problem is it? What treatment may work best? Once started, how well is the treatment working?

Once your doctor puts on the detective hat, few discoveries offer as many basic clues as a sample of your blood. That's why some doctors are enthusiastic about pulling out the hypodermic needle to get a few milliliters of your blood.

But I've long been concerned about the overuse of taking blood samples -- and I'm specifically talking about overuse here. As I point out in my recent book, "The New Prescription," if you went to any group of people -- those in your company break room, the patrons in a restaurant -- and took blood samples from all of them, nearly everyone would have something in their blood that would interest an inquisitive doctor. Some vitamin or mineral or chemical or enzyme or other natural substance would be too high or low or at just the edge of normal. The doctor could then spend hundreds or thousands of dollars pursuing this finding further -- but ultimately not make a diagnosis or prescribe any particular treatment. People have needless biopsies, CT scans and other testing every day after an unnecessary blood test opens the door to a concern -- and these can lead to major costs and complications.

Here's another complication, reported in the Archives of Internal Medicine. Researchers looked at more than 17,000 patients with heart attacks who were treated in hospitals across America. Twenty percent of the patients developed moderate to severe hospital-acquired anemia. Those who developed anemia parted with a significantly greater volume of blood from sampling (174 versus 84 milliliters). For each 50 milliliters (about 1.7 ounces), the risk of anemia went up by 18 percent. Anemia, in which the blood isn't carrying enough oxygen around the body, is often caused by blood loss.

Does parting with a few ounces of blood present a dire threat to everyone's health? Probably not, given that blood donors are allowed to give several pints a year. But when you're in the hospital after a heart attack, do you want anything else creating a threat to your well-being unless it's for a really good reason? No.

This Bloomberg story contained this quote from a physician: "Some doctors indiscriminately take blood tests without consciously asking why they need it and what they're looking for. It's hard to change when they get into the routine of doing things." One option, the story pointed out, is for doctors to test a single sample multiple times instead of going back to the well to satisfy each question.

In addition, it's wise for all of us, patients and doctors alike, to remember that blood-drawing is a medical procedure (called phlebotomy) that comes with benefits and risks like any other procedure. It's also to your benefit to know what tests you're getting -- and why.

For more on how to get better health and need the health care system less, check out Dr. Cynthia Haines' book, The New Prescription: How to Get the Best Health Care in a Broken System (HCI Books, Dr. Cynthia Haines and Eric Metcalf). This is a book about getting what you really want: better health on your own terms. More medical care doesn't mean better health. Dr. Cynthia Haines and Metcalf reveal some of the most egregious problems with a medical system gone awry, opening readers' eyes to how to better navigate the changes underway. Using solid research, insiders' insights, and patient anecdotes, they offer cost-effective and potentially life-saving ways to get more out of health care while using less of it. Find Dr. Cynthia Haines on Facebook @, the Dr. Cynthia Haines YouTube channel, and