What should investors do during a market downturn? Some might resort to panic selling, but that's hardly a good strategy. Unless a company's investment thesis has changed because of recent developments, market downturns aren't a good enough reason for most investors to sell.

For those who can afford it without blowing their budget, it's actually a great idea to pick up shares of top companies on the dip during a correction. With that in mind, here are two excellent growth-oriented companies to buy in the ongoing market meltdown: tech giant Alphabet (GOOG -2.65%) (GOOGL -2.31%) and medical device maker DexCom (DXCM 5.06%).

1. Alphabet

President Donald Trump's tariffs threaten to send the economy into a recession. If that happens, Alphabet, Google's parent company, could suffer. Alphabet makes the bulk of its revenue from advertising. During challenging economic times, consumers and businesses spend less -- companies are likely to decrease their ad budgets, harming Alphabet's results. So the tech giant's near-term prospects seem uncertain, but investors looking at the next five years and beyond should consider pouncing on this opportunity.

Alphabet's long-term prospects remain intact thanks to its dominance in search, strong cloud computing and artificial intelligence (AI) businesses, and leadership in other markets like video streaming. To unpack just some of that, Alphabet is the runaway leader in online search. While some thought the rise of sophisticated AI chatbots would put a significant dent in its search empire, that turned out to be an opportunity for the company. Alphabet added an "AI overview" to its search results.

Alphabet is still generating massive ad revenue. The cloud segment is also on fire, driven by the increased adoption of various AI applications it offers. Furthermore, streaming still has miles of growth left, and Alphabet's YouTube is a leader in the niche. The company's cloud and video streaming businesses ended 2024 with a $110 billion annual run rate; it had expected to cross the $100 billion mark in these departments at the beginning of 2024.

Lastly, Alphabet benefits from a wide moat based in part on network effects from its search engine and YouTube, and an incredibly valuable brand name. The stock might indeed suffer in the short run depending on what happens to the economy, but it should still deliver outsized returns to patient investors. That's what makes Alphabet a top stock to buy in the correction.

2. DexCom

DexCom could see its costs rise and its bottom line and margins shrink -- at least in the short run -- due to Trump's tariffs, since some of its manufacturing sites are spread worldwide to support its international expansion efforts. DexCom is still building new facilities in countries such as Ireland and Malaysia. That said, the diabetes-focused healthcare company also has significant manufacturing capacity in the U.S., where it generated 28% of its revenue in 2024.

In my view, the medical device leader should be fine, even if tariffs force it to pass some of these higher expenses on to consumers. DexCom remains a leader in the market for continuous glucose monitoring (CGM) systems, which are devices that allow diabetes patients to track their blood glucose throughout the day. The adoption of this technology has been a significant growth driver for DexCom, yet plenty of growth fuel remains for at least three reasons.

First, third-party payers are increasingly opting to cover CGM devices, making more patients eligible for reimbursement. As the company's CEO, Kevin Sayer, said during its fourth-quarter earnings conference call: "In the past two years alone, reimbursement for CGM has significantly expanded as we've helped establish our clinical value well beyond insulin management."

Second, even among reimbursed patients, many have yet to opt for CGM in some markets, including the U.S.

Third, there are vast swaths of the world where CGM technology isn't yet accessible. As DexCom's main competitor, Abbott Laboratories, pointed out two years ago, only about 1% of adults with diabetes worldwide have access to CGM technology. While DexCom does not do business in many of those places, there's still significant room to reach new patients through expansion efforts, just as it has done throughout the years.

Lastly, the medical device specialist benefits from the network effect. The more its installed base of diabetes patients grows, the more third-party companies will make devices and accessories for diabetics compatible with DexCom's, including insulin pens, pumps, and more. So DexCom should remain a leader in this niche for a long time, and take advantage of the white space ahead while delivering excellent revenue and earnings growth.