Dr. Barbara Wasson, DAc
The other common reason you would feel tired after a treatment is if your body is already run down and "deficient". When you get acupuncture it draws on your energy stores to get your body to heal. If you are already low on energy then you will feel the draw even more, again, making you sleepy after treatment.
If I were you I would have a conversation with your acupuncturist so they can determine why this is happening and if they need to adjust their treatment strategy a bit. I find some of my patients can handle a more aggressive treatment and some need a lesser approach. Communication is key to figuring this out.