Are Drug Store Blood Pressure Machines Accurate?

March 30th, 2015

It seems these days you can't walk into a grocery store or a pharmacy without seeing a free blood pressure machine tucked away in a back corner.

As kids, we all used to beg our parents to let us give them a try, just because they were fun and free. But many individuals rely on these free machines in order to make critical decision about their health, whether for the convenience, or because the cost of seeing a health professional is just too high.

Are drug store and grocery store blood pressure machines reliable enough to bear such a responsibility?
Are Drug Store Blood Pressure Machines Accurate?


Blood Pressure & How It's Measured



Simply put, blood pressure is a measure of the force of your blood pushing against the walls of your arteries each time your heartbeats. According to WebMD, when your heart contracts and pumps blood through your veins, the pressure exerted on blood vessel walls is called systolic pressure. The pressure on the vessel walls between these heartbeats is called diastolic pressure. A standard, healthy blood pressure of 120/80 mm Hg (millimeter of mercury, a manometric unit of pressure) equates to 120 mm HG systolic pressure and 80 mm HG of diastolic pressure.

You've no doubt had your blood pressure taken many, many times before - at nearly every visit to the doctor's office and each trip to the hospital. Typically, a nurse or doctor will wrap a velcro cuff around your upper arm, which is then inflated either electronically or by using a hand pump. The cuff grips your arm tightly as it inflates.

Then, the medical professional opens the valve of the cuff and allows the pressure to slowly fall. As soon as the blood pressure machine detects the sound of your blood pulsing, your systolic pressure is recorded. Eventually, the sound of your blood pumping disappears entirely; at which point your diastolic pressure is recorded.

At least, that's how many electronic blood pressure monitors work. Though they have become the norm, some medical practices still utilize manual blood pressure monitors, which measure the actual physical pressure inside the cuff itself.

Debating the Accuracy of Free Blood Pressure Monitors



Many publications and individuals have investigated the accuracy of drug store and pharmacy blood pressure monitors, with most concluding that their results are to be taken with a grain of salt.

According to Mayo Clinic, drug store monitors are "not accurate enough to make health decisions regarding your blood pressure."

They note that, while free blood pressure machines may start off accurate, these machines need regular maintenance and recalibration in order to stay that way. It's hard to say whether a free blood pressure machine inside a Walgreens or CVS has been properly cared for. Testing and calibration should be done about twice per year, or more if problems arise, but this process often isn't regulated properly.

The blood pressure cuffs on most free machines are often too small, as well. Mayo Clinic notes that the inflatable portion of the cuff should cover at least 80 percent of the upper arm for a proper reading, but free machines are usually outfitted with one-size-fits-all cuffs that don't adjust to fit individuals. For this reason, free machines may be most accurate for medium sized individuals, and less so for people with very large or very tiny arms. Standard cuffs found on free blood pressure machines are too small for about 37 percent of the population.

But what does it all mean? Let's talk impact.



One study from American Family Physician in 2005 noted that an average free blood pressure device classified 23 percent of normal blood pressure individuals as hypertensive, and 16 percent of hypertensive individuals as normal.

An informal study done by CBS Pittsburgh tested 10 different machines in Walmart, Kmart, CVS, and others. The study found two of the 10 machines were off by more than 15 points when compared with a simultaneous reading done by a medical professional.

Another study done by Good Housekeeping tested a number of pharmacy blood pressure machines in the New Jersey area. Of 22 total readings, they found 10 were off by more than five points when compared to readings taken by a registered nurse practitioner.

Alternatives to Free Blood Pressure Machines



While blood pressure machines inside drug stores, pharmacies, and grocery stores are convenient and free, and though they may serve as a helpful reference point, it's imperative to get regular, accurate readings in order to properly make health decisions.

The best option is to visit your doctor or another medical health professional in order to get a reading from their industrial grade, properly maintained equipment.

Many experts also recommend home and portable blood pressure monitoring systems for a more accurate and relatively inexpensive solution. The Ozeri CardioTech unit, for example, retails for around $59.95 and comes highly recommended via over 600 Amazon reviews. Omron also makes several well-reviewed home blood pressure monitors that retail for about $60.

Regardless of how and where you get your blood pressure measured, ensure you're following best practices for an accurate reading. Many free blood pressure machines in pharmacies do not display these standard guidelines, so be sure to remember them for your next visit:

Sit in a chair with your back supported
Uncross your legs
Keep feet flat on the floor
Support your reading arm at heart level
Remove your shirt or roll up your sleeve to provide a bare arm
Rest for at least 5 minutes before a reading
Do not use caffeine or tobacco within 30 minutes of a reading
Do not take a blood pressure reading when abnormally stressed
For ensured accuracy, take several readings in one sitting, about a minute apart

A normal or healthy blood pressure averages about 120/80 mm Hg. Hypertension is defined as any reading higher than 140/90. If you think you may be suffering from high blood pressure, consult a medical professional to develop a treatment plan.