Michael Hector has committed his future to Reading after signing a new three-year contract with the Championship club.
Watford have confirmed the signing of Austria defender Sebastian Prodl from Werder Bremen.
Manager Peter Taylor has moved to bring in Hewitt with current right-back Michael Harriman away on international duty with the Republic of Ireland Under-21 squad.
Highly-regarded Hewitt, 19, signed for Ipswich from Macclesfield in the summer of 2012 but has not yet nailed down a regular first-team place at Portman Road, making 12 appearances.
He will now look to add to his experience at Priestfield, starting with Saturday's League One trip to Sheffield United.