Homeopathic Potency Scale Explained

Several potency scales are in use in homeopathy. Hahnemann created the centesimal or "C scale", diluting a substance by a factor of 100 at each stage. The centesimal scale was favored by Hahnemann for most of his life. A 2C dilution requires a substance to be diluted to one part in one hundred, and then some of that diluted solution diluted by a further factor of one hundred. This works out to one part of the original substance in 10,000 parts of the solution.] A 6C dilution repeats this process six times, ending up with the original material diluted by a factor of 100−6=10−12. Higher dilutions follow the same pattern. In homeopathy, a solution that is more dilute is described as having a higher potency, and more dilute substances are considered by homeopaths to be stronger and deeper-acting. The end product is often so diluted that it is indistinguishable from the dilutant (pure water, sugar or alcohol).

There is also the continued flow mode of dilution that is measured on MFC.

Hahnemann advocated 30C dilutions for most purposes (that is, dilution by a factor of 1060). In Hahnemann's time it was reasonable to assume that preparations could be diluted indefinitely, as the concept of the atom or molecule as the smallest possible unit of a chemical substance was just beginning to be recognized. We now know that the greatest dilution that is reasonably likely to contain one molecule of the original substance is 12C, if starting from 1 mole of original substance.

This bottle contains Arnica montana (wolf's bane) D6, i.e. the nominal dilution is one part in a million (106).

Some homeopaths developed a decimal scale (D or X), diluting the substance to ten times its original volume each stage. The D or X scale dilution is therefore half that of the same value of the C scale; for example, "12X" is the same level of dilution as "6C". Hahnemann never used this scale but it was very popular throughout the 19th century and still is in Europe. This potency scale appears to have been introduced in the 1830s by the American homeopath Constantine Hering. In the last ten years of his life, Hahnemann also developed a quintamillesimal (Q) or LM scale diluting the drug 1 part in 50,000 parts of diluent.] A given dilution on the Q scale is roughly 2.35 times its designation on the C scale. For example, a preparation described as "20Q" has about the same concentration as one described with "47C"g. Potencies of 1000C and above are usually labelled with Roman numeral M and with the centesimal 'C' indicator implied (since all such high potencies are centesimal dilutions): 1M = 1000C; 10M = 10,000C; CM = 100,000C; LM (which would indicate 50,000C) is typically not used because of confusion with the LM potency scale.

The following table is a synopsis comparing the X and C dilution scales and equating them by equivalent dilution. However, the homeopathic understanding of its principles is not explained by dilution but by "potentisation", hence one cannot assume that the different potencies can be equated on the basis of equivalence of dilution factors.

X Scale C Scale Ratio Note
1X 1:10 described as low potency
2X 1C 1:100 called higher potency than 1X by homeopaths
6X 3C 10−6
8X 4C 10−8 allowable concentration of arsenic in U.S. drinking water[11]
12X 6C 10−12
24X 12C 10−24 Has a 60% probability of containing one molecule of original material if one mole of the original substance was used.
26X 13C 10−26 If pure water was used as the diluent, no molecules of the original solution remain in the water.
60X 30C 10−60 Dilution advocated by Hahnemann for most purposes: on average, this would require giving two billion doses per second to six billion people for 4 billion years to deliver a single molecule of the original material to any patient.
400X 200C 10−400 Dilution of popular homeopathic flu preparation Oscillococcinum
Note: the "X scale" is also called "D scale". 1X = 1D, 2X = 2D, etc.