Pat J. Dixon, 58, a nurse in Atlanta, takes five medications to lower her blood pressure. In many ways, Ms. Dixon is typical of a patient who develops resistant hypertension. At 5 feet and 172 pounds, she is obese, and her weight gain has caused mild Type 2 diabetes, for which she takes yet another drug. The diabetes is an extra strain on the kidneys, in turn worsening her blood pressure.

Ms. Dixon said that she did not use much salt when she cooked but that she did like to snack on potato chips.

“My doctor tells me about every week that I’m going to eat myself to death,” she said. “You do kind of get worn out and depressed every morning that you have to take five or six pills.”

The new report is one of the first to help doctors recognize and manage this growing group of difficult cases. Because so few studies have focused on resistance, the authors say, the number of drug-resistant patients is unclear.

By reviewing studies of patients with at least some hypertension, the panel estimated that 20 to 30 percent could not control their blood pressure with three or more drugs, even when taking them exactly as prescribed. The 20 to 30 percent cohort appears to be growing. A large study in 2006 from Stanford found that the number of blood-pressure patients who were prescribed three or more drugs had increased over 12 years, to 24 percent from 14 percent.

If patients need that many drugs, experts say, they are likely to be at greater risk for illness even if they lower their blood pressure to normal. These patients have usually had high blood pressure for some time and, as a result, have more organ damage.

“It’s a critically important issue,” said Dr. Sheldon Hirsch, chief of nephrology at Michael Reese Hospital in Chicago. “One of the biggest failings in medicine is that as we increasingly realize the importance of treating hypertension, that lower numbers are better than higher numbers, we have increasing trouble reaching those goals.”