ZocDoc is looking to bring its online platform to every state in the contiguous U.S. by the end of this year. At the moment, the company covers 40% of the U.S. population across 2,000 cities and towns, and more than five million patients use the company’s free service each month.

In addition, ZocDoc has also broadened its reach by working with the country’s most forward-thinking hospitals and health systems across 20 different states. During 2013, they’ve increased hospital and health system client base by nearly 200%, and over the last year – ZocDoc began to facilitate enhanced patient access to major health systems such as BJC HealthCare, Hartford HealthCare, Main Line Health, Meridian Health, and Sentara Healthcare.

According to a recent survey by Merritt Hawkins, the national average wait time to see a physician is 18.5 days, and as high as 45 days in cities like Boston. In sharp contrast, the majority of patients who use ZocDoc see a doctor in just 24 – 72 hours. The company manages to accomplish this by revealing what it calls the “hidden supply” of care — the 10 to 20 percent of appointments that are cancelled last minute — thereby optimizing doctors’ schedules and offering their availability to patients in real time.

The ZocDoc service is free for patients via ZocDoc.com or the free ZocDoc app for iPhone and Android.