As with many medicines, placing CBD under the tongue for 1-2 minutes is recommended, this provides maximum absorption via capillaries in the mouth.
Immediately swallowing CBD oil may offer less absorption due to the acids in the stomach breaking it down before it is taken up by the body.
Some people find that swallowing CBD oil can leave a harsh taste at the back of the throat. By holding it under the tongue and letting it absorb gradually, this is minimised. Another solution for those who find the taste harsh is to follow it with a light snack, or a spoonful of honey.