The Food and Drug Administration has given the green light to most forms of medical-related mobile apps. It says it will normally only regulate those apps which replace or complement some standalone medical devices.

The FDA’s announcement aims to clarify the legal position of medical apps. Depending on how you interpreted the law, it was arguable that all medical apps were covered by the agency’s regulatory powers and had to comply with complicated technical restrictions. That created the risk that some app developers might be deterred from innovation.

After a consultation process that began more than two years ago, the FDA has now formally confirmed it will adopt a policy on enforcement discretion in most cases. That means that even where it may have a legal power to regulate an app, it usually won’t do so. The policy goes beyond simply having an unspoken agreement and part of the idea is that it should be enough to satisfy potential investors in app firms who want to be confident that regulation won’t be a risk.

The FDA will now only enforce the rules for two types of app. One is where an app effectively turns a mobile device into a regulated medical device, for example when combined with a case that turns a phone into an electrocardiogram machine.

The second is when an app is designed to work alongside an existing regulated device, for example as a tool for inspecting and interpreting an X-ray image.

In both these cases, the apps will be subject to risk-based review by the FDA in the same way as specialist devices. To date the agency has already reviewed and approved 75 mobile applications, less than half a percent of those available.

According to the FDA official responsible for devices, the principle is that the agency should be ” reviewing only the mobile apps that have the potential to harm consumers if they do not function properly.”

The agency also noted that it doesn’t have any regulatory powers over the manufacturers of phones or tablets (unless they have the relevant medical technology built in), nor does it have any control over app stores themselves (rather than individual app developers.)