Jeff Williams introduces the new Apple Watch capable of taking an FDA-approved electrocardiogram at the company's annual product launch, Wednesday, Sept. 12, 2018, in Cupertino, Calif.

Morgan Stanley's estimate is that health for Apple will top $15 billion in sales by 2021, based on the popularity of the Apple Watch and its health features, like monitoring heart rate and steps. The very high end of Morgan Stanley's estimate range is $313 billion by 2027, which is a particularly lofty figure since Apple's total revenue last year was $266 billion.

It's a nascent space for Apple and hard to predict how much money the company will make from health services as it potentially dives deeper into monitoring features such as blood glucose and blood pressure , the investment bank wrote on Monday.

Apple's opportunity in health care is so large with the Apple Watch that the company should soon generate tens of billions of dollars a year in annual revenue from wearables and health services, according to a new report from Morgan Stanley.

"At the mid-point, Apple's health efforts could result in ~$90B of annual revenue by 2027, roughly ~35% of its current revenue base," the report says.

Apple has a few key advantages over its technology rivals, including Alphabet and Microsoft, as it looks to move into the medical market and attack the $3.5 trillion health-care industry, the report says. Privacy is among the most important benefits. For instance, Apple was able to recruit 400,000 people in less than a year for its Apple Watch heart health study with Stanford University, suggesting that people are willing to share their medical information with Apple.

Beyond consumer device sales, the company has started to sign deals with health insurers who are willing to pay for some portion of the Apple Watch on behalf of their members. Apple has already inked that type of partnership with Aetna. It's also currently in talks with private Medicare plans, which could mean increased access to the Apple Watch for seniors.

"Medicare has the most concentrated pools of money and is the least complicated to navigate," the Morgan Stanley analysts wrote.

The company also has revenue potential in the electronic medical records market.

IPhone users will have access to the Apple's health app, which allows customers to pull together medical information from dozens of hospitals and clinics. In its current form, the feature is designed for consumers, because it's a huge challenge for people to aggregate their lab reports, immunization records and more.

Morgan Stanley said it could turn into a real business if Apple starts pulling together data and selling reports to health systems. To maintain consumer trust, Apple would have to effectively pitch it as a way for hospitals and clinics to gain insights into broad populations while protecting the data of individual patients.

The report listed five other things Apple could do that would generate a lot of investor interest:

Introduce new medical wearables.

Add medical grade monitoring, like sleep, blood glucose or blood pressure.

Make the Apple Watch readily available through insurance companies as a benefit that's reimbursed.

Start its own employer joint venture or join a group like Haven, which currently consists of Amazon, J.P. Morgan and Berkshire Hathaway. Apple already runs its own employee medical clinics, dubbed AC Wellness.

Acquire a health care company.

Apple has publicly stayed mum about those topics, and a company spokesperson declined to comment on the report.