The "white coat" phenomenon - where blood pressure rises due to nervousness in front of a medic - is much more obvious when patients stand in front of doctors, the study found. This can lead to too many people taking unnecessary drugs, according to the researchers.
The study, published in the British Journal of General Practice, found that readings taken by doctors were higher (by a blood pressure value of 7/4mmHg) than when the same patients were tested by nurses.
Led by the University of Exeter Medical School, the analysis included blood pressure readings from 1019 people whose measurements had been taken by both doctors and nurses.
Dr Christopher Clark, from the school, said the findings should lead to changes in how blood pressure is taken.
He said: "Doctors should measure blood pressure as part of a routine check-up, but not where decisions on blood pressure treatment depend on the outcome.
"The difference we noted is enough to tip some patients over the threshold for treatment for high blood pressure, and unnecessary medication can lead to unwanted side effects.
"Some patients may be asked to continue to monitor their own blood pressure at home, which can build anxiety. These measures could all be avoided by someone other than a doctor taking the blood pressure recording."