Lowe limped off after 20 minutes of Ireland’s 42-21 victory over England at Twickenham last weekend and will now miss the home games against Wales (March 6) and Scotland (March 14).
New Zealand-born Lowe, 33, earned his 45th cap against England following his debut in 2020 and has been a key part of coach Andy Farrell’s set-up in recent years.
He was, however, left out of the defeat by France in Paris that kicked off the 2026 campaign, before returning to play in the win over Italy in the side's second fixture.
Ireland are third in the Six Nations table, six points behind leaders France.