Those enrolling in the federal healthcare exchange to receive coverage starting Jan. 1 will get an extra day to sign up.
The Obama administration extended the deadline to midnight Tuesday, recognizing that high demand may impact a customer's ability to enroll. Thirty-six states, including Virginia, rely on the federal website for enrollment. The remaining 14 states and the District of Columbia have their own exchange websites.
"Anticipating high demand and the fact that consumers may be enrolling from multiple time zones, we have taken steps to make sure that those who select a plan through tomorrow will get coverage for Jan. 1," Julie Bataille, a spokesperson for the Centers for Medicare and Medicaid Services, which runs the site, told NBC News.
Residents in D.C. still have until midnight Monday to sign up while those in Maryland have until Dec. 27.
Early Monday, an alert on the Healthcare.gov website warned users that high demand could cause some delays.
Customers calling in for coverage have reported wait times of nearly two hours. But there are some who are finding success on the federal and state exchanges.
"I got a call yesterday saying I was approved," said Oliver Mitchell of Maryland.
President Barack Obama announced Friday that insurance sign-ups have soared across the country in December, following upgrades to the troubled website.
"It's certainly better than what it was in Oct. and Nov. In Oct, just 100,000 people had signed up on both the state and federal exchange.... We might end up getting to 1.2 or 1.5 million by the end of this month," NBC's Senior Political Editor Mark Murray said.
The numbers aren't where the administration hoped they would be thanks to early problems with the website during the initial roll-out of the Affordable Care Act, but Murray says the rise in applicants does show that the law is starting to get people to sign up.
The Obama administration also has taken steps to help the 500,000 consumers with canceled policies who have yet to secure new coverage.
More than 4 million people lost coverage because their policies fell short of new federal standards. This happened despite Obama's repeated and now discredited pledge that people happy with their insurance could simply keep it. He partnered that assurance with a promise that people happy with their doctors could keep them, too. Not so, in many cases.
After a wave of cancellations, the government revised its rules on substandard policies to let insurance companies offer them for one more year. It's not clear how many plans will be retrieved from the dustbin as a result. Some Americans will be allowed to buy bare-bones catastrophic plans. And people who lost their insurance can shop for new plans that in many cases will offer better terms. But better coverage will often come at a higher monthly cost.
Each policy is priced based on a ranking of bronze, silver, gold or platinum. The bronze options have the lowest monthly premiums but include high deductibles -- an average of more than $4,300, according to an analysis of marketplace plans in 19 states by Avalere Health. A consumer who upgrades to a silver plan could reduce the deductible to about $2,500. A top-of-the-line platinum plan has the lowest average deductible: $167.
Those who don't sign up for coverage by the end of this week will not be covered at the start of the year, but they have until the end of March to sign up and avoid a fine for being uninsured.