US social network for doctors Doximity says it has doubled in size since April and now lays claim to 100,000 members.

Doximity, which has been feted in the tech press as a 'Facebook for doctors', says that two years after launch it is now used by over 15 per cent of US physicians.

CEO Jeff Tangney said: "For an industry that traditionally takes 17 years for new ideas to spread across the country, this is a milestone we're not only very proud of but also something that should get both providers and their patients very excited.

"Healthcare is long overdue for a digital revolution, and Doximity is helping physicians take the lead in this transformation."

Its recent growth spurt positions Doximity as a serious challenger to more established US online physician networks such as Sermo, which launched six years ago and has 130,000 members.

Doximity was set up by the founders of mobile healthcare software company Epocrates and allows doctors to stay in touch and collaborate on patient treatment.

It also makes much of its secure, 'medical-grade' messaging system and offers doctors a free digital fax service, as well as the chance to earn honoraria payments for research, second opinions, and medicolegal consulting.

Doximity's plans include the launch of an API that should allow it to offer users new third party applications and services.

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