Doctors are using a method called pre-disease to do that.
Pre-disease are conditions where tests are edging toward full blown illness, but are not quite there yet.
It's a red flag that may lead people to the doctor to reduce their chances of the actual disease and its complications.
38-year-old Esther Neil-Thomas had no family history of high blood pressure. Her doctors, though found something when they checked her pressure on several occasions.
"They said that it's borderline high blood pressure," she said.
Borderline high blood pressure or hypertension, is what doctors call pre-hypertension. It means patients such as Esther are at higher risk of heart attacks, strokes and death.
"Even if you remain in that pre-disease state for a lifetime, you're still at higher risk of disease," said Dr. Egenia Gianos, with NYU Langone Medical Center.
Normal blood pressure is 120/80 or less. High blood pressure is 140/90 or more.
Anywhere in between, say 125/86, is pre-hypertension. The closer to 140/90, the higher the risk for complications.
Blood tests to define pre-diabetes are not standardized. As with pre-hypertension, numbers are somewhere in between normal and full-blown diabetes.
As with blood pressure, pre-diabetics are at higher risk for complications than those with normal blood tests.
"You should be concerned about pre-diabetes if you have a family history of diabetes, two is if you're overweight," said Dr. Loren Wissner.
Overweight is a risk for both pre-diabetes and pre-hypertension, and reducing risk means lifestyle changes for both, too.
Family history of high blood pressure is also something that should make someone see a doctor to check for pre-hypertension.
The sooner doctors can diagnose people at risk, the sooner they can treat to prevent complications of the diseases.