This mudra should be attempted only under the guidance of an expert teacher (Guru).
Close the mouth. Roll the tongue backward so that the normally lower surface touches the upper palate. Try to take the tip of the tongue as far back as possible without strain. With practice, the tongue will automatically ascend into the sinuses to stimulate many vital nerve centers in the brain.
The tendon beneath the tongue must be slowly cut, week-by-week. Various surgical methods or a sharpened stone can be utilized for this purpose. Massage the tongue by milking it for long periods of time daily. Continue for many months until it is possible to touch the eyebrow center with the tip of the tongue. When the tongue has reached the required elongation, full khechari mudra can be practiced. Fold the tongue towards the back of the mouth. Carefully slide it through the upper back cavity in the palate as far as it will go.
If khechari mudra is performed during physical exercises, a bitter secretion may be tasted. This can be harmful. The practitioner is therefore advised to discontinue this mudra if a bitter secretion is tasted.
It removes the feeling of thirst and hunger. Yogis, who are buried under the ground for long periods of time, perform khechari mudra for the whole duration. This allows them to retain their breath for as long as they wish without harming themselves. This mudra awakens the kundalini shakti and also helps to preserve the vital energy of the body.