Club moss (Lycopodium clavatum) is a herb from folk herbalism. Modern studies find no health benefit. Alkaloids like lycopodine attracted some research interest, but no recognized medical use has emerged.
You might find it sold as glycerites, liquid extracts, or powders. Benefit claims are unproven, so standard dosing does not exist.
The alkaloids can be toxic to the liver and nervous system, especially with long-term use. Avoid club moss if you are pregnant, nursing, or scheduled for surgery. Check with a healthcare professional before using it.