Someone with high blood pressure that's controlled on diet or medication may notice a spike in blood pressure at the doctor's office.
Other patients may have these spikes more than once in a while.
A report in a journal called "The Lancet" Saturday says spikes of blood pressure may increase stroke risk, but it's not a black or white issue.
Helga Long has high blood pressure, the kind that fluctuates from one time she takes it to another.
"I measure it at home twice a day and it can go from 130 to 160," explained Helga Long, a woman with fluctuating high blood pressure.
Those kinds of ups and downs don't cause any symptoms of headache or dizziness, but the new report says that patients such as Helga may be more at risk for a stroke than patients whose blood pressure is stable on medication.
Dr. Samuel Mann is a high blood pressure specialist, and he says this is only one of many studies on fluctuating blood pressure.
Many say it's risky, many say it's not.
"Intuitively, we would all think that greater variation contributes to the risk, but we don't know," said Dr. Samuel Mann, of NY Presbyterian Weill Cornell.
One of the dangers, says Dr. Mann, is over treating.
In someone whose pressure is well controlled on drugs, but has high readings in the office, treating that occasional spike can sometimes push a doctor to raise a drug dose.
That can lead to overmedication on most days, and drug side effects.
Though the study showed that spiking blood pressures happened more as people aged fluctuating blood pressure affected stroke risk most for younger patients.
Women had more fluctuating pressures than men.
Other risk factors were smoking and diabetes.
But, since Dr. Mann says there are just as many studies saying the problems doesn't mean more strokes as studies that do, he looks at patient's average readings rather than the spikes.
"If a person's pressure is usually normal and occasionally high, we don't treat it unless a person has symptoms with it or is very severely elevated," said Dr. Mann.
Dr. Mann says stress is a factor in high blood pressure.
There are some people whose pressure will go up moderately with stress, and other people whose pressure will skyrocket.
Experts say they are not sure if the latter group is more at risk for a stroke or if they should be treated.