A flat dosage of 100 ug per person is used commonly in human LSD research. This dosage quantity is convenient to remember because it doesn't take body weight into consideration. A dosage of 100 ug per person typically results in dramatic symptoms, but the threshold for activity generally is placed at 20 ug LSD per person.
Very low doses of LSD (4-40 ug per person) were tested in human volunteers by Greiner and colleagues in 1958. Psychic changes were established by way of interviews and measurement of pupil size, heart rate, and galvanic skin response. The data below showed that mood and psychomotor effects were detectable in human volunteers at dosages as low as 4 ug LSD per person, which is approximately 0.05 ug/kg of body weight, or 10 times less than the effective dose according to E. Rothlin and Hofmann. The objective measures showed that the galvanic skin response (GSR) was activated after only 7 ug LSD per person. There was a dose-dependent increase in pupil size, heart rate, and other parameters.
The researchers observed sudden shifts in affect in the volunteers after 4 ug, 7 ug, or 12 ug of LSD per person, but no significant changes in thought process or content. This data puts the threshold dose for LSD intoxication at about 20 ug per person.
LSD is one of the most potent drugs known to man. Whereas most drugs are administered at doses of tens or hundreds of milligrams, LSD is active at tens or hundreds of micrograms. The potency of LSD is best compared to other drugs on a log scale, as shown in Figure 1 below. Note that the concentration of an active dose of alcohol is about a million times as great, expressed in terms of weight, as the concentration of LSD.
Of course, the effective dose of LSD depends highly on the person, set, and setting. The dose threshold may be lower for people who are generally inexperienced with drugs, and higher for alcoholics and drug addicts.
“Familiarity with other drugs which produce psychological changes is also relevant. Alcoholics and drug addicts seem better able to cope with the LSD experience than normal subjects. I have had more difficulty with anxiety and panic in normal subjects than in patients who have had long experience with drugs.” (Hoffer,A. 1965)Fasting or not can change the effective LSD dose too. Plasma concentrations of orally ingested LSD were twice as much on an empty stomach. The amount of the meal as well as the pH of the stomach will influence LSD absorption.
GREINER T., N. R. BURCH and R. EDELBERG (1958). Psychopathology and psychophysiology of minimal LSD-25 dosage; a preliminary dosage-response spectrum. A.M.A. Archives of Neurology and Psychiatry 79, 208-210.
HOFFER A. (1965). D-Lysergic Acid Diethylamide (Lsd): a Review of its Present Status. Clinical pharmacology and therapeutics 6, 183-255.
Passie T., J. H. Halpern, D. O. Stichtenoth, H. M. Emrich and A. Hintzen (2008). The pharmacology of lysergic Acid diethylamide: a review. CNS Neuroscience & Therapeutics 14, 295-314.