Unfortunately, double blind studies of acupuncture are impossible (the person doing it must know if they're putting needles in), and single blind studies are almost impossible (the patient can feel the needles, and tell how far in they are). The only thing than can be tested is the traditional Chinese medicine chi flow idea, and even assuming there's no chi flow along meridians, that doesn't mean the special locations it tries to explain aren't valid for some other reason. But it can't be tested.

It's all deeply frustrating. I tried acupuncture a few years ago (at a doctor's recommendation) and did a lot of reading. It didn't work for me, unsurprisingly - about the only thing it's been shown to have any effect for is some types of lower back pain, and my pain was (is) mostly in my hands.