WebMD pulled within one million unique visitors (UV) of Everyday Health, tightening the UV horserace between the two companies, according to comScore’s numbers for March.

The Everyday Health network slid from 24,717 million UV in January, to 22,112 in March, while the WebMD network experienced a minor increase over the same period – from 21,185 million in January to 21,210 in March. Everyday Health has measured number one among online health networks – in terms on comScore’s UV count – since last October, after the company merged with Revolution Health. However, Everyday Health’s numbers have slipped since then, and now WebMD is knocking on the door.

Measured as a singular, individual website destination, WebMD.com is ahead by over 10 million UV at 13,418 million, compared with EverydayHealth.com at 3,137 million UV, according to comScore.

Yahoo! Health, AOL Health and About.com Health rounded out the top five for March, at 10,829 million, 10,006 million, and 9,443 million UV, respectively, according to the comScore data.