He may also be absent for the game at Gillingham on Saturday February 25.
This is 19-year-old Keogh's first U-21 call, having previously been a regular with the U-19 side.
Ireland's U-21 coach Don Givens said: "We are looking forward to competing in this tournament in Madeira. We had great success here in 2004, when we won the competition, and we hope that we can repeat that performance.
"I am delighted to welcome the new players to the squad, and hope that this experience will stand to them as we look forward to the draw for the UEFA Under-21 European Championships later this week."
The first game of the tournament is against Madeira on Tuesday February 14.
Squad in full: Colin Doyle (Birmingham City), Darren Quigley (UCD), Keith Keane (Luton Town), Gerard Nash (Ipswich Town), Paul McShane (Brighton and Hove Albion), Marcos Painter (Birmingham City), James Hand (Huddersfield Town), Shane McFaul (Notts County), Gary Dicker (UCD), Michael Collins (Huddersfield Town), Michael Timlin (Fulham), Willo Flood (Manchester City), Stephen Ireland (Manchester City), Stephen Foley (Bournemouth), Stephen Bradley (Drogheda United), Aiden McGeady (Celtic), Stephen Ward (Bohemians). Andy Keogh (Scunthorpe United), Mark Yeates (Colchester United), Roy O'Donovan (Cork City).