"I don't know as of today what his plans are, but there's a very real concern", she told Britain's ITV television. This is a historic moment.
Provided that Markle senior doesn't make to the ceremony, there are a number of possible replacements who can walk Meghan down the aisle instead.
Eric Marquez, 40, from OH, is one of several passengers on a bus tour offering a cream tea while they drive past key sights including Harry's home at Kensington Palace.
Meghan Markle's dad Thomas is recovering from surgery.
Last weekend, Britain's press watchdog issued an advisory note to editors asking media to stop following Thomas Markle, warning that he was being pursued daily.
On Tuesday, the school, based a few blocks from the famous Sunset Boulevard, held another special event to commemorate the wedding, gathering students into the courtyard to celebrate with glasses of lemonade while waving British and American flags.
It is still not clear who will walk Ms Markle down the aisle, but her mother Doria Ragland has arrived in London.More news: Banned ozone-destroying gas may still be in production
When she lived with her mother Doria Ragland in Los Angeles, the actress spent a great deal of time with Mr Markle who now lives in Mexico. She also accompanied Meghan at the Invictus Games closing ceremony, hosted by Prince Harry, which took place in Toronto.
Along with the Mulroneys, this will be the first royal wedding they have ever attended.
Meanwhile, Meghan's mum Doria Ragland has touched down in the United Kingdom to be by her daughter's side.
He reportedly told TMZ he didn't want to cause further embarrassment to his daughter and the royal family, but then appeared to reverse course and told TMZ a day later he would attend the wedding.
His latest position followed a paparazzi scandal, in which he embarrassed Meghan and the royals by admitting that he accepted money to stage tabloid photographs in the run-up to the wedding.
He told celebrity website TMZ that doctors would clear any blockage, fix damage and "put a stent where it is needed".
But on Monday he missed a call from his daughter and she later told him she loved him in a text message and was concerned about his health.
The publication says the 73-year-old is "alert and coherent" but it's as yet unknown how long he will need to stay in hospital.