  This paper investigates the global existence of solutions to Keller-Segel
systems with sub-logistic sources using the test function method. Prior work
demonstrated that sub-logistic sources $f(u)=ru -\mu \frac{u^2}{\ln^p(u+e)}$
with $p\in(0,1)$ can prevent blow-up solutions for the 2D minimal Keller-Segel
chemotaxis model. Our study extends this result by showing that when $p=1$,
sub-logistic sources can still prevent the occurrence of finite time blow-up
solutions. Additionally, we provide a concise proof for a known result that the
equi-integrability of $\left \{ \int_\Omega u^{\frac{n}{2}}(\cdot,t) \right
\}_{t\in (0,T_{\rm max})}$ can avoid blow-up.
