Obamacare's opportunity for insurers? A bunch of new customers. The risk? Insurers have no idea how healthy these people are.
The danger of unexpected costs from benefits claims by enrollees in the Affordable Care Act is leading many insurers to try to get a sense of their health status as quickly as possible—both to encourage preventive care for at-risk customers and to better price next year's premiums, health industry insiders said.
To that end, insurers are deploying strategies to figure out just who is enrolled. They range from introductory phone calls, mailings, prompts on social media, and even to cash incentives to get customers to disclose details of their health, or to go to the doctor to get checked out.
As of the end of February, more than 4.2 million people had enrolled in private insurance plans sold on government-run Obamacare exchanges, which close their enrollment period March 31. Many of those people were previously uninsured, increasing the level of uncertainty facing insurers.
"The insurance executives understand this is a brand new group of customers they know very little about," said Ceci Connolly, managing director of the Health Research Institute at PricewaterhouseCoopers. "So they have been devising a number of ways to proactively reach these customers and learn about these customers' health status."
(Read more: Obamacare: ACA enrollment just 4.2 million by Feb )
When insurers have an understanding of new enrollees' health status, "they're better positioned to help manage conditions, especially chronic conditions," Connolly said.
She cited the example of a newly insured person who is unaware of a diabetic condition. The person's first encounter with the health-care system would likely be in an emergency room—much more expensive than a simple screening at a doctor's office.
But if insurers get that person medically screened before they go into diabetic shock and uncover their condition, "you have a fighting change of educating them, giving them some tools to manage it, and having a much better quality of life and reducing the cost to everybody," she said.
That includes not just costs to the individual customer and the insurer. All customers of insurance plans could end up paying more in premiums if their fellow enrollees submit benefit claims that threaten insurers' profit margins this year.
In a report last month about Obamacare's implications for insurers, Swiss Re noted that the mandate that nearly every American have some form of insurance by 2014 carries "growth opportunities" that are accompanied by "high uncertainty."
The report said that "with a new pool of consumers purchasing coverage on the exchanges, insurers are likely to price cautiously to avoid losses, at least until more is known about the new pool of customers."
Milka Kirova, a senior economist at Swiss Re, said insurers are "monitoring very closely the demographics and socioeconomic profiles" of the consumers who have signed up for their plans as the companies try to figure out what these customers could end up costing in benefit claims.
"They're running these models and they're trying to get an early read of the risk profiles of the people they've gotten," Kirova said.
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Estimating that risk quickly is important because insurers very soon must set their pricing for premiums that take effect next year. But a number of insurers aren't depending on guesswork to figure out, and possibly control, their future costs.
In Pennsylvania, the insurer Independence Blue Cross has "started an outreach program to welcome" new enrollees, said company spokeswoman Judimarie Thomas.
"In the first step we are calling new members and inviting them to ask questions about their health plans, and we are also asking a few basic health questions," Thomas said. "Over the next few months we will continue to contact new members through mail and email with information on our wellness programs, our online tools and resources, on how to use the medical benefits and prescription coverage, and other important programs or benefits."
"Where appropriate, we will refer new members to our medical management programs or encourage them to see their primary care doctor," Thomas said.
Another "Blue" taking a proactive approach is in Florida.
Jon Urbanek, a senior vice president at Florida Blue, said, "When people sign up with us, they're definitely going to get some electronic communication." In most cases they're getting a welcome call.
Those communications offer new enrollees free biometric screenings—measuring weight, blood pressure, cholesterol and other physical levels—which can be performed by a nurse at one of the the insurer's 17 retail locations.
"We don't put these things in the passive sense, we want them to be used," Urbanek said.
"The population that we're seeing on the [Obamacare] exchange, they are skewing older, they're skewing a bit more female, and from risk pool perspective, we anticipate right now that they are higher risk," Urbanek said. That makes it even more important to get those enrollees to undergo biometric screenings, so any health problems can be revealed and possibly addressed, he said.
"If we can get people more involved in their health care, that's one of the things that ultimately is going to have an impact on cost," he said.
Urbanek said the insurer is seeing 5 to 7 percent of enrollees accept the offer for free screenings—which tracks the rate seen by insurers nationwide who make similar offers.
But he noted that this is "significant and dramatic when you think about the dollars that are spent on health care."
In New York state, new insurance company Oscar has seen a much higher adoption rate with a program that pays new enrollees $10 to answer 10 questions related to their health, called "10 for 10." That health risk assessment questionnaire takes as little as five minutes to fill out.
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Oscar's co-founder Kevin Nazemi said that about 67 percent of enrollees have taken up Oscar on the offer, and answered the questionnaire.
"This gives an early warning to us, and enables us to do proactive outreach," he said.
—By CNBC's Dan Mangan. Follow him on Twitter @_DanMangan