Let K = Q(θ) be a number field generated by a complex root θ of a monic irreducible trinomial of type F (x) = x 2 r + ax m + b ∈ Z[x] and Z K its ring of integers. In this paper, we study the monogenity of K. More precisely, when m = 1, we provide some explicit conditions on a, b, and r for which K is not monogenic. We also construct a family of irreducible trinomials which are not monogenic, but their roots generate monogenic number fields. To illustrate our results, we give some computational examples.