Sometimes the placebo is in the form of a pill (sugar pill), but it can also be an injection (saline solution) or consumable liquid.
In most cases, the person does not know that the treatment they are receiving is actually a placebo. Instead, they believe that they are the recipient of the real treatment. The placebo is designed to seem exactly like the real treatment, yet the substance has no actual effect on the condition it purports to treat.
But the placebo effect is much more than just positive thinking. When this response occurs, many people have no idea they are responding to what is essentially a "sugar pill." Placebos are often utilized in medical research to help doctors and scientists discover and better understand the physiological and psychological effects of new medications.
– verywellmind.com