If you don't meet the qualifications for being a blood donor, I beg you, please stop donating blood. This is not a joke. I have a close friend who died after contracting an infection from a contaminated blood transfusion. There is a reason that blood banks screen donor applicants. Lying on the questionnaire and using the donation process for your own health needs is just selfish. It's one thing to engage in illegal activity that doesn't harm others (as many justify steroid use), but in this you are putting the lives of others at stake.
You may think the risk to a recipient is small, but these questionnaires are not meaningless. Blood banks can only test for a limited number of possible infections and must rely heavily on the screening process to minimize the risks of transfusions. By lying about your drug use, you are denying the recipient the right to make an informed decision about the risks of accepting a blood transfusion.
If you want to reduce your blood count, see a doctor and get a phlebotomy. Yes, it will cost money, but if you are doing this for your own health, why shouldn’t you pay? Don't try to convince yourself that this is a victimless crime. The innocent recipient who contracts a potentially fatal illness would vehemently disagree. Why should someone else pay (in health risk) for your vanity?