What if my blood sugar’s too high today? Is it time for my blood pressure pill? With nagging text messages or more customized two-way interactions, researchers are trying to harness the power of cell phones to help fight chronic diseases. “I call it medical minutes,” says Dr. Richard Katz of George Washington University Hospital in the nation’s capital. The trend is called mobile health or, to use tech-speak, mHealth. If you’re a savvy smartphone user, you’ve probably seen lots of apps that claim to help your health or fitness goals — using your phone like a pedometer or an alarm clock to signal when it’s time to take your medicine. Katz and other researchers are going a step further, scientifically testing whether more personalized cell phone-based programs can link patients’ own care with their doctors’ disease-management efforts in ways that might provide lasting health improvement. After all, most of the population now carries a cell phone. Accessing the Internet with them is on the rise, too — nearly 40 percent of cell callers do, the Pew Internet & American Life Project reported last week — allowing more sophisticated digital health contact. On the other hand, older adults are less likely to use smartphones. So are people who are sicker, with multiple chronic diseases, says Dr. Joseph Kvedar, director of the Center for Connected Health, a division of Boston’s Partners Healthcare. Kvedar notes that nearly any phone can handle simpler text-messaging programs. Among the biggest offered to date is the free text4baby, where government-vetted health tips timed to pregnant women’s due dates are texted weekly to about 50,000 participants so far.