The users of medicinal cannabis in The Netherlands are advised by the Office of Medicinal Cannabis to prepare cannabis tea as follows: "add 1.0 g of cannabis to 1.0 L of boiling water and let simmer for 15 min. Filter out solid parts by using a common tea- sieve. Tea can be consumed immediately, or stored in a closed bottle in a refrigerator for up to 5 days."

Researchers of the University of Leiden investigated the cannabinoid composition of this tea. They found that tea prepared with different batches of cannabis with an overall THC concentration (phenolic THC + THC acid) of 19.7 per cent showed only a moderate variation in THC concentrations of 15 per cent. The mean concentration of THC was 10 mg per litre and of THC acid (THCA) 43 mg/L. In the plant THC is mainly present as THCA and is converted into the psychotropic THC upon heating (baking, smoking, boiling). Since with cooking of water only a relatively low temperature of 100 degrees Celsius is reached only a small part of THCA was transformed into THC, resulting in an availability of only about 5 per cent phenolic THC of the whole THC (10 mg of 197 mg THC acid + THC). The authors also found, that the THC concentration rapidly declined during storage, which was largely prevented by the addition of coffee creamer powder.

(Source: Hazekamp A, Bastola K, Rashidi H, Bender J, Verpoorte R. Cannabis tea revisited: A systematic evaluation of the cannabinoid composition of cannabis tea. J Ethnopharmacol 2007 May 24; [Electronic publication ahead of print])