Winners tend to keep on winning. And make no mistake about it: DexCom (NASDAQ:DXCM) is a winner.

During its 21 years in business, the medical-device maker has transformed how individuals manage diabetes. DexCom's market cap now stands at close to $40 billion. The company generated nearly $1.5 billion in sales last year. Its profits are growing. Could DexCom even be a millionaire-maker stock? 

Woman with dollar signs next to her head

Image source: Getty Images.

Looking back

There could very well be some investors walking around today who have already become millionaires thanks to buying DexCom stock. The company conducted its initial public offering (IPO) in April 2005. An investment of around $28,250 back then in DexCom would now be worth a little over $1 million. 

Less than a year after its IPO, DexCom launched its first continuous glucose monitoring (CGM) system. In 2007, the company rolled out an even better CGM that could be used for up to seven consecutive days. Over the next few years, DexCom unveiled new generations of CGM technology.

In 2015, the company launched its G5 CGM in September. For the first time, individuals could monitor their glucose levels on their smartphones and other smart devices. That set the stage for DexCom's most impressive innovation to date -- the G6 CGM. Introduced in 2018, the G6 eliminated the need for the inconvenient fingersticks that glucose monitors required previously. 

It's hard to overstate just how important the G6 CGM was to DexCom's fortunes. In the 13 years prior to the launch of the product, its share price increased sixfold. During the two years or so after DexCom won FDA clearance to market the G6, the healthcare stock has soared seven times higher.

Tremendous growth opportunities

Even after its impressive success in the past, DexCom still has tremendous growth opportunities. The company estimates that no more than 40% of Americans with type 1 diabetes currently use CGM systems. Of Americans with intensive type 2 diabetes that requires insulin, only around 15% use CGM systems. That gives DexCom ample room to grow in the important U.S. market. 

But the company's prospects are even greater outside the U.S. More than 460 million adults worldwide have diabetes. It's estimated that only 6% of them are able to live without complications resulting from their condition.

And the opportunities continue to grow. In the U.S. alone, around 1.5 million new cases of diabetes are diagnosed each year.

DexCom hopes to capture more of this expanding market with its G6 CGM. It also plans to launch the G7 CGM next year. This new device will be smaller and less expensive than the G6, which should enable DexCom to gain additional market share. 

Millionaire-maker?

So could DexCom turn investors who buy the stock now into millionaires? It depends on several factors, including your initial investment size and how long you're willing to wait.

If you had $500,000 or more to invest in DexCom, I'm confident that the stock would make you a millionaire within the next few years. Of course, most people don't have that much money to invest, especially in a single stock.

Let's say that you instead have $10,000 that you could use to buy DexCom shares. Your initial investment would need to multiply by 100 times to reach $1 million. Will DexCom be a 100-bagger over the next decade or even the next 20 years? Probably not.

However, DexCom should continue to be a winner for a long time to come. I think it's a great stock to buy right now. But if you want to be a millionaire, you'll probably need to add more winning stocks to your portfolio.