Google is letting patients share electronic medical records with loved ones or care providers who may be needed to help in emergencies.
The decision to let people selectively allow others to glimpse medical profiles results from feedback it has gotten since Google Health medical records service was launched in May 2008.
"One issue we hear regularly is that people want help coordinating their care and the care of loved ones," Google product manager Sameer Samat said in a message posted at the California firm's website.
"They want the ability to share their medical records and personal health information with trusted family members, friends, and doctors in their care network."
Google Health now has a "share this profile" feature that permits chosen people to view, but not alter, online medical records.
"A few years ago, my father suffered a minor heart attack and was sent to the emergency room," Samat wrote.
"I arrived on the scene in a panic, and was asked what medications he was taking. I had no clue. If my father had a Google Health account, and had shared his profile with me, I would have been up-to-date on his current medications."
Renewable links to health records are uniquely tailored to each recipient and automatically expire after 30 days, according to Google.
"You can stop sharing at any time, and you can always see who has access to your information," Samat said.
"Those who are viewing your profile can only see the profile you share, not any other one in your account."
Benefits of electronic health records have been touted by US President Barack Obama and are believed by analysts to strongly appeal to "Baby Boomers", the generation of Americans born between the late 1940s and early 1960s.
Microsoft rolled out a HealthVault online medical records storage and management service in October 2007.
Privacy advocates worry that online medical information is vulnerable to tampering or snooping, possibly from insurance companies or employers out to reduce liabilities by shunning those with health issues.
Google said it built a secure computer platform separate from its search system to host medical records as part of an emphasis on keeping health information protected.
Google vice president of search product and user experience Marissa Mayer said at the launch of Health that it was built with "our highest level of security."
Google Health has links to pharmacies, clinics and diagnostic labs.
The service is free and enables people to have electronic copies of information such as prescriptions, lab test results, hospital stays, and medical conditions stored on Google computers.
People can link heart monitors to Google Health so vital statistics can be fed to a heart attack assessment services online.
A "virtual pillbox" will also automatically send alerts to people's mobile telephones, reminding them when it is time to take medicines.
Users of the service dictate how the information is shared.