In this paper, we study the signed k-domination and its total version in graphs. By
a simple uniform approach we give some new upper and lower bounds on these two
parameters of a graph in terms of several different graph parameters. In this way, we can
improve and generalize some results in literature. Moreover, we make use of the wellknown
theorem of Tur´an [On an extremal problem in graph theory, Math. Fiz. Lapok 48
(1941) 436–452] to bound the signed total k-domination number, γt
kS(G), of a Kr+1-free graph G for r ≥ 2.