This paper deals with unbounded solutions to the following zero-flux chemotaxis systemwhere α > 0, Ω is a smooth and bounded domain of R n , with n ≥ 1, t ∈ (0, Tmax), where Tmax the blow-up time, and m1, m2 real numbers. Given a sufficiently smooth initial data u0 := u(x, 0) ≥ 0 and set M := 1 |Ω| Ω u0(x) dx, from the literature it is known that under a proper interplay between the above parameters m1, m2 and the extra condition Ω v(x, t)dx = 0, system ( ) possesses for any χ > 0 a unique classical solution which becomes unbounded at t ր Tmax. In this investigation we first show that for p0 > n 2 (m2 − m1) any blowing up classical solution in L ∞ (Ω)-norm blows up also in L p 0 (Ω)-norm. Then we estimate the blow-up time Tmax providing a lower bound T .