Acupuncturists have a choice in terms of how long the acupuncture treatment is. Different times have different clinical effects.
Most often, the acupuncture needles are retained in the acupuncture points for 20-30 minutes. Traditionally we say it takes 30 minutes for the qi, the body’s energy, to circulate in the channels.
But if it is an acute situation, such as a back spasm, it is generally better to leave the acupuncture needles in for 15 minutes or less. This is because the muscles will relax quicker in an acute injury like a back spasm.
When the energy is weak, what we call qi deficiency, it is better to leave the needles in for a longer period of time, such as 35 or 40 minutes in some cases. This provides and opportunity for the body to work on improving the energy.
When using electro-acupuncture, as I often do for pain, 20 minutes has been shown to be the optimal amount of time for pain relief and reduction of inflammation.