What happened

Insulet (NASDAQ:PODD) stock rocketed 27.3% higher in May, according to data from S&P Global Market Intelligence. Shares have pumped out a gain of 38% in 2019 through June 3. 

The Massachusetts-based company is the leader in tubeless insulin pump technology with its Omnipod pump.

Insulet stock's May performance is even more impressive when you consider that the market had a terrible month. The S&P 500, including dividends, fell 6.4% in May, and is down 10.4% so far this year.

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 strong performance last month to the company's May 4 release of first-quarter 2019 results, which were better than Wall Street and many investors were expecting, and to management increasing full-year 2019 revenue guidance. Shares popped 12.3% on the day following the release and continued to move higher throughout the remainder of the month.

PODD Chart

Data by YCharts.

In Q1, Insulet's revenue grew 29% year over year to $159.6 million, surpassing the $154.7 million Wall Street was looking for. Earnings per share came in at $0.07 -- versus a loss of $0.11 per share in the year-ago period -- breezing by the consensus estimate of $0.01. The quarter marked only the third time in its history that Insulet has posted positive quarterly earnings, with the previous two quarters being the first two times.

Now what

For the second quarter of 2019, Insulet guided for revenue growth of about 29% to 33% year over year. And for full-year 2019, it expects revenue to increase about 18% to 22% year over year, up slightly from its previous outlook of 17% to 22% growth. The company doesn't provide earnings guidance.

Insulet has a history of beating its revenue guidance, so there seems to be a good chance it could exceed these growth figures.