That could give some financial professionals the entree into crypto they have long craved. If you’ve been suffering from FOMO lately, just imagine their fear of missing out.

Millions of individual investors already own bitcoin or other digital currencies. Many have racked up gains of 400% or more over the past year. Alongside that, the stocks and ETFs that advisers typically recommend can feel like fossils.

In a recent survey by Bitwise Asset Management, an investment firm in San Francisco, 81% of financial professionals said clients had asked in the previous 12 months about investing in crypto. Nearly three-quarters said clients already own, or might own, digital assets.

Only 9% said they already have put some of their clients’ assets in cryptocurrency. But 17% of the financial professionals who haven’t yet bought any crypto for clients said they would in 2021—more than double last year’s number.

“Advisers feel the pressure,” says Ben Cruikshank, head of Flourish, a subsidiary of Massachusetts Mutual Life Insurance Co. “They feel the need to offer things clients are looking for, even if it makes them uncomfortable.” Flourish provides specialized financial services to advisers, including making cryptocurrency available for their clients.

The advent of bitcoin-related ETFs in the U.S.—the ProShares fund is likely the first of many—makes offering crypto easier for advisers. It also lets them earn fees on it.

So will a new service from Interactive Brokers Group Inc., an online brokerage based in Greenwich, Conn. The firm announced this week that it will permit financial professionals to trade bitcoin and several other digital currencies through its platform.

Interactive Brokers acts as a custodian—safekeeping assets, handling trades and maintaining records—for more than 5,700 advisers with a total of $60 billion in clients’ assets.

Its new service will enable advisers to buy crypto for their clients and report it on the same account statement as conventional assets like stocks, bonds and ETFs.

Interactive Brokers’ chairman, Thomas Peterffy, tells me that “we did get hundreds of calls from [advisers] and are following up, while new calls keep coming in.”

Until now, financial professionals generally haven’t been able to manage clients’ digital assets alongside other holdings. That’s made it hard to know how much risk their clients are taking, how to minimize their taxes and how to help them plan for retirement. Services like Interactive Brokers’ new offering should change that.

One adviser found out not long ago that a client who held $3 million in assets with him also had $11 million in crypto, says Tyrone Ross, chief executive and co-founder of Onramp Invest Inc., a San Diego-based firm that helps advisers with digital-asset management.

Maybe you’ve never owned any cryptocurrency and don’t want to. Maybe you haven’t yet but you might. Maybe you already do. What should you be on the lookout for if your financial adviser brings it up?

First, beware of anyone flogging a new bitcoin-related ETF. The new ProShares fund and those sure to follow don’t hold digital currency; instead, they own futures contracts, whose returns can deviate widely from it. ETFs owning bitcoin itself haven’t arrived yet in the U.S.

Most advisers should understand that; one who nevertheless recommends a bitcoin futures fund is probably “just a salesperson, not someone focused on your long-term goals,” warns Mr. Ross.

Be on guard against “people making absolute guarantees about the future,” says Mr. Cruikshank. “You wouldn’t accept grandiose claims based on only a few years of data in any other asset class, and you shouldn’t with crypto either.”

Adding crypto to your portfolio, whether you do it or your adviser does, requires both of you to start from scratch.

Even a small allocation to digital currency can transform your entire portfolio’s risk and return. Has your tolerance for risk changed? How much, and why? Your investment policy statement, which explains your portfolio’s goals and how your assets are positioned to achieve them, needs to be revised. So do your financial plan and your estate and retirement plans.

If buying crypto is your idea, your financial advisers are just doing their job if they ask you to review these documents with them first.

If buying crypto is their idea, then it’s your job to say “no” if it makes you uncomfortable.

If you and your advisers together decide to buy some crypto, insist that they review your risk tolerance. They should also revise your investment policy statement to mandate monthly reviews of your crypto holdings and redraft your financial plan to account for the new strategy. Make sure they discuss how it would fit in your overall portfolio and square with your financial objectives—rather than just how it might jack up returns.

Finally, urges Mr. Ross, ask the most important question of all: “How do you get paid on it, and what will it cost me?”

Write to Jason Zweig at [email protected]