Acupuncture needles do come in a variety of lengths and gauges, for most people they are relatively painless upon insertion, and have very little resemblance to hypodermic needles (the kind used to draw blood). There may be a slight pricking sensation (similar to a mosquito bite) as the needle is inserted, but many people don’t feel it. The sensation of qi gathering or being dispersed at the acupuncture point is often experienced as a feeling of heaviness, warmth, or fullness. A tingling sensation along the course of the associated meridian can be felt if you’re sensitive to energy-flow.