The company said it sold 4.5 million wearable fitness devices in the quarter, up from 1.72 million in the year-earlier period. Fitbit's gross margin came in at 47 percent.
"Our second-quarter results included our highest quarterly revenue in the eight-year history of Fitbit," said James Park, Fitbit co-founder and CEO, in a statement.
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Fitbit projects revenue of $335 million to $365 million in the third quarter. It also sees adjusted earnings in a range of 7 cents to 10 cents per share and gross margin of 47 to 48 percent.
"If you had to nitpick here, there are a couple of things. In the guidance, the revenue growth rate does slow, as one would expect. The margins for next quarter are also a little lower than what we saw in 2Q," said Bob Peck, an Internet analyst at SunTrust Robinson Humphrey, in a CNBC "Closing Bell" interview Wednesday.
Fitbit touted its growth in international markets, where sales spiked 250 percent year over year. Revenue soared about 300 percent in both Europe and Asia.
"I think one of the things that we saw was the company could not make the products fast enough. I think there was a little supply constraint which impacted the gross margins," said Mark Sue, a technology analyst at RBC Capital Markets, on "Closing Bell."
He added that "they're gaining rapid market share" even as more competitors enter the wearable health category.