The Royal College of Nursing Foundation will use the money to provide support to frontline nurses facing hardship.
It is the biggest donation made by a social media company to date to a British organisation involved in tackling the pandemic.
The gift is part of a wider $325m (£257m) worldwide fund the Chinese firm has set up to provide relief.
Not all that sum is being given away in the form of cash. A total of $125m is being offered in the form of ad credits, which are being divided up between small-to-medium sized businesses, non-governmental organisations, local authorities and health bodies.
TikTok and other social media firms are currently facing increased scrutiny over their efforts to tackle misinformation about Covid-19 on their platforms.
This is “an extremely sensitive public policy moment for them all,” commented Carl Miller, research director of the centre for the analysis of social media (CASM) at the think tank Demos.
“Platforms like Facebook and Twitter and TikTok have become our public space.
“They know they are on another frontline themselves [and] governments may well legally require the tech giants to deal with misinformation.”
TikTok’s action follows a pledge by Twitter’s chief executive to donate $1bn of his personal stake in digital payments firm Square to fund “Covid-19 relief”. Jack Dorsey described it as representing 28% of his financial worth.
In April, Facebook pledged $25m to support healthcare workers on the frontline, as well as matching $2m in donations to relief efforts and a further $100m grant to small businesses. The social media company has also donated its emergency reserve of 720,000 masks to healthcare providers.
TikTok intends its move to be seen as a show of solidarity with nurses, many of whom have posted videos to its platform over the past month.
Videos featuring the hashtag #NHS have had over 189 million views on the app, with the top search results featuring hospital nurses and doctors dancing to popular music.
“Despite the huge challenges frontline healthcare workers face on a daily basis, I have been enormously heartened by what we are seeing on our platform,” said the tech firm’s UK general manager.
Health secretary Matt Hancock said: “I’m delighted that TikTok is supporting the RCN Foundation which brings so much support to so many.”
Last week, culture secretary Oliver Dowden ordered social media companies to be more aggressive in their response to so-called fake news, particularly to conspiracy theories linking 5G networks to the pandemic.
But politicians also rely on the same platforms to get their messages across.
TikTok has widely promoted a video of the Mayor of London Sadiq Khan thanking healthcare workers in its Discover feed.
And the health secretary himself has posted a video to the app.
Using the hashtag #ThankYouNHS, Mr Hancock told frontline staff about the work the government was doing in regard to protective equipment and testing, and thanked them for their efforts.
“Politicians are in a weird state with the tech giants,” commented Mr Miller.
“On the one hand sooner or later they’ll have to regulate them. On the other hand the digital world is one of the most important arenas where they have to campaign.”