Coffee can not only wake you up and get you moving in the morning, but it can also offer you various health benefits. On the other hand, coffee can sometimes do more harm than good if you have high blood pressure. In fact, a new study found that for these particular people, drinking two or more cups each day can seriously increase the risk of death.

The study that was published by the Journal of the American Heart Association involved more than 18,570 participants in Japan—over 6,570 men and 12,000 women—who were all between 40 and 79 years old. During the study, each participant underwent examinations related to their health and answered questionnaires that covered any past health conditions or issues as well as their lifestyle and diet.

After follow-ups over a 19-year span, it was found that 842 participants died due to cardiovascular-related causes. Beyond that, those behind the study noted that while drinking one cup of coffee each day didn’t seem to increase the risk of a cardiovascular-related death for participants who had high blood pressure, drinking two or more cups of coffee each day had a significantly different outcome. In that case, it doubled the risk of cardiovascular-related death for those who had higher blood pressure as opposed to people who didn’t drink coffee.

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“These findings may support the assertion that people with severe high blood pressure should avoid drinking excessive coffee,” said the study’s senior author Hiroyasu Iso, M.D., Ph.D., MPH, in a statement to the American Heart Association. Iso is also the director of the Institute for Global Health Policy Research, Bureau of International Health Cooperation, National Center for Global Health and Medicine in Tokyo, and a professor emeritus at Osaka University. “Because people with severe hypertension are more susceptible to the effects of caffeine, caffeine’s harmful effects may outweigh its protective effects and may increase the risk of death,” he continued.

“This study emphasizes the need to assess all beverages and foods that someone with high blood pressure is consuming in order to optimally manage blood pressure levels,” Michelle Routhenstein, MS, RD, CDE, CDN, heart health dietitian at EntirelyNourished, tells Eat This, Not That! “In my practice, I have individuals assess their body’s response to caffeine, particularly coffee. If their blood pressure values increase within three hours of consumption, we decrease to the appropriate dose or choose more optimal beverages for blood vessel health.”

When it comes to why two or more cups of coffee per day might potentially lead to negative outcomes for those with severe hypertension, Routhenstein explains that “coffee can increase blood pressure up to three hours post-consumption in certain individuals.”

“When blood pressure rises in individuals with severe hypertension, it can cause more life-threatening events such as stroke, heart attack, or an aortic aneurysm,” adds Routhenstein.

Although this study found that drinking one cup of coffee each day didn’t have the same results, Routhenstein still warns against excessive coffee consumption in those with high blood pressure.

“It is important that blood pressure is monitored in response to coffee consumption in all individuals, and especially those with uncontrolled, severe hypertension,” advises Routhenstein. “If there is an increase in blood pressure after consuming one cup of coffee, it may be best advised to avoid it completely.”