What happened

Shares of Insulet (NASDAQ:PODD) declined 11.9% in October, according to data from S&P Global Market Intelligence. The S&P 500 returned 2.2% last month.

The Boston-area healthcare company is the leader in tubeless insulin pump technology with its Omnipod pump.

A two-pane image with the top pane showing an Omnipod attached to a woman's lower stomach and the bottom pane showing the handheld control for the device.

Image source: Getty Images.

So what

We can attribute Insulet stock's weak performance last month to several downgrades from Wall Street firms. All of the rating changes were from buy to hold (or the equivalent, as firms use different terminology).

Insulet didn't release any negative news last month, so we can probably attribute these downgrades to analysts simply believing the stock had gotten a little overheated, as it's been on a tear this year. Going into October, it had been up a whopping 108% for the year, versus the broader market's 20.6% return. Even after October's 11.9% pullback, the stock is still 85% in the green in 2019 through Nov. 1, making it a top-performing medical device stock. 

Insulet stock been surging this year because it continues to pump out strong quarterly results and increase its outlook. After the company's August release of its second-quarter results, the stock soared more than 21%. In Q2, revenue jumped 43% year over year to $177.1 million, breezing by the $164 million Wall Street consensus estimate. And earnings per share landed at $0.02 -- versus a loss of $0.03 per share in the year-ago period -- meeting analysts' expectations.

Now what

Investors don't have long to wait for material news. Insulet is slated to release its third-quarter results after the market closes on Tuesday, Nov. 5.

For Q3, the company guided for revenue growth of 15% to 20% year over year. And for full-year 2019, it expects revenue to jump 24% to 27% -- a solid increase from its prior expectation of 18% to 22% growth. The company doesn't provide earnings guidance.