Diabetes is a chronic disease in which blood glucose levels go unregulated, often rising to dangerously high levels. Unfortunately, it’s become more common in the United States, with more than 29 million people currently afflicted. If they don’t already have it, many of them risk high blood pressure (hypertension) and cardiovascular disease. Doctors may recommend antihypertensive treatments to treat these conditions, but new research published in the British Medical Journal suggests this is a bad idea, as doing so might lead to adverse effects or even death.

For their analysis, researchers at Umeå University in Sweden collected data from 49 published and unpublished studies involving nearly 74,000 participants. Their goal was to investigate the effects of intensive blood pressure-lowering drugs on diabetes patients. “Since we used only aggregated data from previous trials, we are unable to disseminate the results of the research to study participants directly,” the researchers wrote.

Nevertheless, their review yielded some surprising results. They found that the effects of antihypertensive medications depended on diabetic patients’ systolic blood pressure — the top number on a person’s blood pressure reading — prior to treatment. Patients with a systolic blood pressure higher than 140 mm Hg before starting treatment experienced a lower risk of death, stroke, heart attack, and heart failure when they underwent intensive blood pressure treatment. These benefits didn’t apply to those whose systolic blood pressure was under 140 mm Hg at the time treatment began; instead, antihypertensive medications increased their risk of cardiovascular death by 15 percent.

Regardless, Mattias Brunstron, main author of the article, said in a statement that it’s still important “to remember that blood pressure lowering treatment is crucial for the majority of people with diabetes whose blood pressure measures above 140.”

Researchers warn that the results are almost exclusively based on data collected from patients with type 2 diabetes who underwent previous antihypertensive treatment, so the findings may not apply to those with type 1 diabetes.

The findings contradict a recent review that suggested treating people with a systolic blood pressure less than 140 mm Hg is associated with health benefits, including a reduced risk of stroke and albuminuria — a condition in which there is too much of the protein albumin in a person’s urine. With such conflicting results, it’s probably best doctors use caution.

“In practice, it is important to remember that undertreatment of high blood pressure is a bigger problem than overtreatment,” Brunstrom emphasized. That said, the researchers also suggested that blood pressure treatment goals in diabetics should be less aggressive than in the general population, since many otherwise healthy people can handle it.

Source: Brunstrom M, Carlberg B. Effect of Antihypertensive Treatment at Different Blood Pressure Levels in Patients with Diabetes Mellitus: Systematic Review and Meta-analyses. BMJ. 2016.