A new study found that one in four people suffering from high blood pressure don’t take their medications properly — either they take them only part of the time, or not at all.

In an editorial accompanying the study by Professor Morris Brown of the University of Cambridge, he states that treating high blood pressure or hypertension has been a "therapeutic success" that has led to the overall decline of stroke, ischaemic heart disease, and heart failure. Yet a fraction of patients who take these drugs were not seeing any positive effects; this phenomena was labelled as "resistant hypertension." This particular study was designed to investigate why drug therapy wasn’t working in these patients.

“A majority of these patients in any secondary/tertiary care centre would routinely undergo many additional tests and procedures in search of the explanation for their apparent unresponsiveness to standard therapy prescribed in primary care,” the authors wrote.

In reality, patients simply weren’t taking their meds properly.

Since the researchers wouldn’t be able to rely only on self-reported answers, they measured urine samples of 208 people with high blood pressure, who went to a specialist hypertension clinic. Out of these, 17 had been referred for renal denervation, 66 for follow-up, and 125 had been referred by their primary care doctors.

The researchers examined traces of the most common blood pressure drugs in the participants’ urine samples, using high performance liquid chromatography-tandem mass spectrometry (HP LC-MS/MS), a type of technique that can measure the amounts of certain drugs or chemicals in urine. They found that 10 percent of the participants weren’t doing the treatment at all, and 15 percent were taking their meds only part of the time they were supposed to. The researchers found that the people who were most likely to not take the medicine at all were those who were referred for renal denervation — nearly 25 percent of this group had no trace of any high blood pressure drugs in their urine.

Thus, the authors conclude that there are “alarmingly high levels” of non-adherence to prescribed blood pressure drugs. And not taking medication properly can lead to some grave consequences. A study published last year found that people who don’t take their anti-hypertensive meds correctly were more likely to have a stroke and die, compared to people who took their medication properly.

“Non-adherence to therapy, and its recognition, is a particular problem in hypertension because of its chronicity and asymptomatic nature,” Brown wrote in the editorial. “That most patients do not take all their drugs all the time was probably predictable. But that 23 percent of those referred for renal denervation have no detectable drug in their urine was a shock.” The researchers believe that the urine testing technique could be one way to begin improving drug therapy among patients who don’t take their medications.