Acupuncturists have a choice in terms of how long the needles are left in the acupuncture points. 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 about 20 minutes. 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. In this case, I retain the acupuncture needles for 30 or 35 minutes total. The first 20 are with electro-acupuncture. The second I remove the electro-acupuncture and twirl the needles. The combination of electro-acupuncture stimulation and manual stimulation I find is effective at pain reduction.