SAN FRANCISCO — Fitbit Inc. made investors' hearts pump a little faster Tuesday by upping the amount it hopes to raise in its much-anticipated initial public offering.

In what could lift a so-far slow year for IPOs, the company told the U.S. Securities and Exchange Commission it intends to price its shares anywhere between $17 and $19 apiece—$3 more than first disclosed—and the amount of shares sold by existing shareholders will go up from 7.5 million to about 12 million.

Fitbit's IPO is just the third to come out of the Silicon Valley pipeline this year, according to media reports.