The S&P 500 is up 15% this year, and there are many stocks that have been performing much better than that. Shares of Hims & Hers Health (HIMS 1.87%) and Viking Therapeutics (VKTX 7.92%) have been some of the hottest healthcare stocks to own in 2023, rising by over 30% this year. And according to analysts, there could be even more upside for them.

1. Hims & Hers

Telemedicine company Hims & Hers focuses on sensitive consumer issues such as hair loss and sexual health. It has carved out a niche nook for itself, with sales soaring over the years.

From less than $83 million in 2019, the top line climbed to nearly $527 million last year. It remains unprofitable, but business has been booming.

This year, the stock is up around 30%, and that's with giving back some gains of late. In May, the company released its latest earnings numbers. Revenue of $190.8 million for the period ending March 31 soared by 88% year over year.

The company also raised its guidance, projecting that revenue might hit $830 million in 2023, which would be 57% higher than last year. Chief financial officer Yemi Okupe calls the company's customer base "resilient" and a key reason the business continues to generate high growth when many others are struggling.

The consensus Street analyst price target for the stock is just over $12, translating into a potential upside of 40% over the next year or so. Analysts have generally been raising their price targets for Hims & Hers in the past few months.

At a market cap of $1.8 billion, it is still a fairly small healthcare business, and it wouldn't surprise me if the stock's value were to continue rising. With some impressive growth, this could be a coveted business to own this year. 

2. Viking Therapeutics

Biotech company Viking Therapeutics doesn't generate any revenue just yet, but its promising pipeline might bring in billions in the future.

Its VK2809 treats non-alcoholic steatohepatitis (NASH), a liver disease that could affect as much as 5% of people around the world. Given the sizable market potential, the drug candidate could generate as much as $3.6 billion at its peak, which may not be until 2038.

It's in phase 2b trials, so it still has a long way to go, and approval is by no means a guarantee. But encouraging trial results have been enough to get investors excited about the stock.

Another asset with loads of potential is obesity treatment VK2735. It's only entering phase 2 trials and could take even longer to obtain approval. But thanks to the popularity of Novo Nordisk's Ozempic, having a weight-loss treatment in development has also likely helped generate bullishness behind Viking's stock. Year to date, its shares are up 64%.

The potential is there for Viking to be a business that's worth much more in the future. Currently, its market cap is around $1.6 billion, but if it can obtain approval for even one of those drugs, the stock could be off to the races. Analysts are bullish on the stock, and with a consensus price target of over $30, it could rise by around 90% from where it is today.

That's not an outrageous upside, but I question if it's realistic for the next 12 months, which is the period that analyst price targets normally cover. With no revenue, and losses continuing to mount, there's still ample risk with Viking. It is burning through cash and might need to raise money to help fund its research and development. That brings with it the risk of dilution and a falling share price.

Viking is a promising stock, but investors should temper their expectations since analysts are perhaps a bit too bullish, at least in the short term.