Western and Chinese medicine agree on the fact that it really works, and that formal studies, using techniques ranging from blood serum analysis to MRI, have documented acupuncture's efficacy in ways that are compatible with Western scientific methodology. The outcomes of many studies suggest that acupuncture is more effective when applied by a skillful practitioner using traditional theories. For life-threatening problems, go to the emergency room. If your situation is not critical, you have nothing to lose. It starts working right away, as soon as the qi sensation is obtained.
People often feel dramatic results during the initial session.
Yes, it is very safe when practiced by a qualified practitioner. Disposable sterile needles and clean needling protocols make the risk of infection negligible. With distal-point styles of treatment, risks are reduced to an occasional small bruise. Acupuncture, as practiced throughout North America, has one of the best safety records of any form of health care. None that are serious.