When she set out to schedule coronavirus tests for six people for a family cruise to the Bahamas, Linda Blackwood said she had to make “about 1,000 phone calls.”

“We’ve spent more time working on this covid stuff than we will be on the cruise just about,” said Blackwood, a pastor’s secretary in the Florida Panhandle.

Her grandchildren, who are too young to be vaccinated against the virus, needed PCR tests within 72 hours of the cruise, which departed Thursday. This left the family searching for a place that could accommodate them on Labor Day. The vaccinated adults had planned to get rapid antigen tests — but the urgent care had run out.

Travelers around the country have run into similar ordeals as demand for testing has increased amid the delta variant surge, school requirements and workplace rules. The Biden administration said Thursday that it has taken steps to expand access to testing.

For travelers, the requirements for testing are ever-changing — and growing.

Blackwood went on her quest just before a new deadline came into play for cruise passengers: Vaccinated cruisers — which is the vast majority of them — need to get a negative test result within two days of boarding as of Sept. 13 under new guidance from the Centers for Disease Control and Prevention.

“I cannot imagine that because this has been hard enough,” she said.

Italy added a requirement on Aug. 31 that even vaccinated visitors need a negative test within 72 hours of arrival, and other European countries are adding new restrictions every day. Canada, which reopened to Americans last month, requires proof of vaccination and a negative molecular coronavirus test within 72 hours.

Many Caribbean islands require testing before arrival, and cruise lines started mandating that even vaccinated travelers get tested last month. Anyone who is flying into the United States needs a test no more than three days in advance.

“It’s part of the new world of travel, and I think it’s something we all have to get used to if we’re wanting to travel,” said Jessica Griscavage, chief executive of Runway Travel, a Virtuoso agency. “It’s so hard right now because each country and each cruise line and each tour operator are going to have their own rules.”

Hawaii’s rules for testing — including type of test and approved providers — have been among the most strict for travelers, though vaccinated visitors from the continental U.S. no longer need tests.

When Jocelyn Guerette and her husband Pete were making plans to visit her mother in Hawaii last month, they thought they scheduled the test for Pete, who is not vaccinated, within the right amount of time. He got tested on the afternoon of Aug. 18, and their plane would land the afternoon of the 21st.

But when he entered his information on Hawaii’s travel site, he discovered his test would expire while he was still on the plane, his wife said in an email. That meant his options included spending 10 days in quarantine or taking another test and waiting for results, rescheduling his flight and losing reservations in Hawaii. “In panic mode,” he found a flight that left during the window when his test was still valid, said Jocelyn Guerette, 55, of Colorado Springs.

“My goodness, it was a mad scramble to find a flight to the islands and beat the clock,” she said.

Testing manufacturers and pharmacies have acknowledged some stress on the system.

Walgreens spokesman Phil Caruso said in an email that the chain’s more than 6,000 testing locations are able to meet demand as more people need to be tested.

“Anecdotally we may experience intermittent delays in supply in some location and continue to work with the all of our testing partners to meet patient demand,” he wrote.

Abbott Laboratories said in a statement that there are tens of millions of its BinaxNOW coronavirus tests — which include home antigen tests observed by a digital health provider that can often be used for travel — “in various settings and supply chains.”

“Nationally, we’re seeing unprecedented demand as case rates rise — and we’ve been scaling up manufacturing since Delta became the dominant strain and new CDC guidance called for a re-prioritization of testing,” the statement said. “We’re working with our customers to ensure tests get to where they’re most needed and we’re ramping back up, as we did last year.”

Companies and travel advisers are trying to help vacationers navigate the rules and any shortages. Royal Caribbean International and Celebrity Cruises are selling approved home kits through their websites. Carnival Cruise Line “is working to set up mobile pre-cruise rapid testing sites at all of its homeports as a back-up alternative for vaccinated guests who aren’t able to make arrangements,” the company said in a statement earlier this month.

Carnival Cruise Line brand ambassador and senior cruise director John Heald said on his Facebook page that he had received hundreds of questions and comments about the new testing requirements.

“I know it is easier for some more than others to get a test,” he said, promising “smiling crew members, cocktails, sunshine and Fun” as a reward.

Jack Ezon, founder and managing partner of the luxury travel agency Embark Beyond, said travelers in big cities typically have an easy time accessing tests.

“It’s when you live in more rural areas that it’s a lot more challenging,” he said.

The agency has medical concierges on staff to help people get tests if they’re having a difficult time, and has partnered with eMed to provide clients with home tests that are supervised in a telemedicine session. He said the company has already been shipping the tests to travelers.

“It’s especially enticing for people who are traveling abroad because they don’t need to worry about ‘Where am I going to go for a pharmacy?’” he said. “Now all you need is literally this small little box and an Internet connection.”

Travel adviser Nicole LeBlanc, owner of Mon Voyage in Dallas, said in an email that she suggests travelers make an appointment for coronavirus testing well in advance — and to be sure of what type of test is required and how long it will be valid.

“Earlier in the summer, it was a bit easier to line up a test at your local drugstore or buy your own kit,” she said. “The Delta variant surge has made the supply somewhat tighter. Now travelers have to be a little more deliberate in their planning.”

She said airport testing is an option if travelers run into delays or supply issues at local testing centers.

“These tests are sometimes (but not always) more expensive, but in many are cases worth it,” LeBlanc said. “Your test will have the longest possible validity if you are taking it the day of your flight.”

For Tonda Walls, 44, of Fredericksburg, Va., the prospect of finding a rapid test one or two days before her Thanksgiving cruise to the Bahamas is worrisome. She said in an email that she’s concerned she might not be able to get an appointment if demand is up ahead of the holiday.

“I of course don’t mind doing it for everyone’s safety,” she said. “It’s just stressful.”