How long do hypertension medications (diuretics vs ace inhibitors vs ca channel blockers vs etc.) take to achieve full effect?

About a day or so: Hypertensive medication have a quick onset of activity. Take your BP meds as directed and then about a day or so take your resting BP. You can buy an automatic BP machine from a drug store to check your own BP. If you BP is still have after a couple of days go back to your doctor and tell him/her. They will likely change your prescription until they have found a solution for your high BP.

Hours to weeks: The oral medications for treating high blood pressure start to work as soon as they are absorbed and the full effect of a single dose occurs within hours. Most blood pressure drugs sustain the reduction in BP for 24 hours so they can be taken once daily. When starting medication or changing dose there may be some further blood pressure reduction over the next several weeks.