Washington ? Medical milestone or privacy invasion? A tiny computer chip approved Wednesday for implantation in a patient’s arm can speed vital information about a patient’s medical history to doctors and hospitals. But critics warn that it could open new ways to imperil the confidentiality of medical records.

The Food and Drug Administration said Wednesday that Applied Digital Solutions of Delray Beach, Fla., could market the VeriChip, an implantable computer chip about the size of a grain of rice, for medical purposes.

With the pinch of a syringe, the microchip is inserted under the skin in a procedure that takes less than 20 minutes and leaves no stitches. Silently and invisibly, the dormant chip stores a code that releases patient-specific information when a scanner passes over it.

Think UPC code. The identifier, emblazoned on a food item, brings up its name and price on the cashier’s screen.

The VeriChip itself contains no medical records, just codes that can be scanned, and revealed, in a doctor’s office or hospital. With that code, the health providers can unlock that portion of a secure database that holds that person’s medical information, including allergies and prior treatment. The electronic database, not the chip, would be updated with each medical visit.

The microchips have already been implanted in 1 million pets. But the chip’s possible dual use for tracking people’s movements, as well as speeding delivery of their medical information to emergency rooms, has raised alarm.

“If privacy protections aren’t built in at the outset, there could be harmful consequences for patients,” said Emily Stewart, a policy analyst at the Health Privacy Project.

To protect patient privacy, the devices should reveal only vital medical information, like blood type and allergic reactions, needed for health-care workers to do their jobs, Stewart said.

An information technology guru at Detroit Medical Center, however, sees the benefits of the devices and will lobby for his center’s inclusion in a VeriChip pilot program.

“One of the big problems in health care has been the medical records situation. So much of it is still on paper,” said David Ellis, the center’s chief futurist and co-founder of the Michigan Electronic Medical Records Initiative.

As “medically mobile” patients visit specialists for care, their records fragment on computer systems that don’t talk to each other.

“It’s part of the future of medicine to have these kinds of technologies that make life simpler for the patient,” Ellis said. Pushing for the strongest encryption algorithms to ensure hackers can’t nab medical data as information transfers from chip to reader to secure database, will help address privacy concerns, he said.

The U.S. Department of Health and Human Services on Wednesday announced $139 million in grants to help make real President Bush’s push for electronic health records for most Americans within a decade.