The original offer of 115p per share was made on October 23, 2020, and recommended by the McCarthy board.
No reasons for the higher price were given and Lone Star added that the offer terms will not be increased again unless McCarthy receives a rival bid.
Shareholders vote on the takeover later today.
In October, Lone Star said that the acquisition offered it an opportunity to move into the UK retirement living sector.
In a statement then, Donald Quintin, president of Lone Star Europe, said: “As a leading developer and manager of retirement communities in the UK, McCarthy & Stone represents an attractive opportunity in a market underpinned by clear fundamentals: a rapidly ageing population and a structural undersupply of suitable housing options for older people."
The US firm had added that it was a long-term and patient investor with significant experience in real estate investing,