If Limerick thought their win over Clare would pave a comfortable passage through their league campaign, they were given a jolt at the Gaelic Grounds on Saturday.
Limerick raced into a three-point lead early on, but were pegged back to level terms after 15 minutes.
The home side edged two points clear again, but points from Andrew Mitchell and Brian Smyth had Westmeath back on terms.
The outstanding James Ryan levelled matters once more late in the first half, before a Richie McCarthy point sent the Treaty men in 0-10 to 0-9 ahead at the break.
Limerick freshened things up at half-time, bringing on Brian Geary and Pat Tobin for Stephen Lucey and Andrew O'Shaughnessy and, within four minutes of the restart the changes proved inspired, Tobin racing clear of several defenders to hit a cracking shot past goalkeeper Pat Burke.
That made it 1-12 to 0-9 and, from there Limerick remained in front without ever playing with any fluency.
Westmeath might have made a better fist of things but were denied goals when Nicky Quaid made two great saves to deny Smyth and Brendan Murtagh.
Ryan shone at centre-forward with Donal O'Grady and Eoin Ryan dominating midfield.
Andrew Mitchell was superb in the Westmeath defence and was ably assisted by Eoin Price, who moved upfield near the finish to pick off two fine points.
Man of The Match -- James Ryan (Limerick).
Scorers -- Limerick: J Ryan, R McCarthy (4f) 0-5 each, E Ryan 0-4 (3f, 1'65'), P Tobin 1-1, D O'Grady, N Maher 0-2 each, A O'Shaughnessy 0-1. Westmeath: A Mitchell 0-4 (1f, 1'65'), D carthy 0-3 (2f), E Price, B Smyth, B Murtagh (1f) 0-2 each, N Flanagan, C Curley 0-1 each.
Limerick -- N Quaid 7; S Walsh 5, S Lucey 6 , D Moloney 7; W McNamara 5, S Hickey 5, P O'Brien 5; D O'Grady 7, E Ryan 7; R McCarthy 6, J Ryan 7, N Maher 5; A O'Shaughnessy 4, K Downes 6, G Mulcahy 5. Subs: B Geary 6 for Lucey (h-t), P Tobin 7 for O'Shaughnessy (h-t), K O'Rourke for O'Brien (67), B Hourigan for McCarthy (67).
Westmeath -- P Burke7; R Whelan 5, P Greville 6, E Price 7; P Gilsenan 5, A Mitchell 7, J Shaw 4 ; N Flanagan 4, C Curley 5; B Smyth 6, D McNicholas 5, B Murtagh 5; A Devine 4, B Leharte 4, S Carthy 5. Subs: J Clarke 5 for Carthy (47), C Mackey 5 for Leharte (50), D Golden for Devine (65), A Prior for Curley (65). Some subs not on long enough to be rated.
Ref -- A Stapleton (Laois).