Thank you for submitting your question. Some diet pills can cause bone marrow suppression and low white blood cell counts. Diethylpropion(Tenuate) and Sibutramine(Meridia) are the two diet pills that can cause low white blood cell counts.
Over-the-counter diet pills that contain ephedra or the fat-absorbing pill Alli do not affect the bone marrow and therefore do not cause low white blood cell counts.
I hope this answers your question.