The 24-year-old rejoined the Silkmen for a second spell in June after leaving Tranmere Rovers and has scored once in 26 appearances this season.
Mackreth has also had spells in non-league with Barrow and Grimsby Town during his career.
He could make his Shakers debut in Monday's game against Sheffield United.
Meanwhile, Macclesfield have confirmed the signing of 24-year-old Laurie Bell, who spent time at Manchester City's academy as a youngster before moving to the USA.
Find all the latest football transfers on our dedicated page.
League One side Bury have signed Macclesfield winger Jack Mackreth for an undisclosed fee on an 18-month deal, with the option for a further year.