Of all the widely available investments in the world, the one that has delivered the biggest gains this year is the virtual currency called bitcoin, which exists online only…isn’t controlled or issued by any bank, brokerage or government…and has become a tremendously volatile form of payment.

This year through September, the price of each bitcoin has more than quadrupled, going from $998 to more than $4,900, up from $1 in 2011.

Along the way, however, it has had drops of more than 80%. It is right only for investors comfortable with big risks…and only in amounts you are willing to lose, perhaps entirely.

Steps to take if you want to delve into bitcoin investing

Wait for a pullback of 25% or more. That has happened every year since 2010—including two drops of about 35% this year—and it ensures that you won’t be getting in at the top.

Buy bitcoins directly. There’s only one SEC-approved fund that invests in bitcoins, Bitcoin Investment Trust (GBTC), but it has traded at more than double the value of its underlying ­assets this year.

Instead, use a reputable dealer such as Coinbase.com, the leading online US platform for buying, selling and storing digital currency. You establish an account and fund it with cash or use a credit or debit card. You can buy a portion of one bitcoin divided out to the eighth decimal place.

Coinbase, which typically charges 1.5% of your transaction amount when you buy or sell, is regulated by state and federal laws on money transmissions. It has insurance covering any losses due to a breach of Coinbase physical security or cybersecurity or employee theft, but not losses due to your own negligence.