Kratom (Mitragyna speciosa) is described as being a stimulant at low doses, and narcotic/sedative at higher doses. Dosages can vary greatly depending on the freshness of the leaf and the potency of the particular plant/strain. Fresh or freshly dried leaves are generally considered the most potent, but dried leaves are most common outside of SE Asia. Following are approximate dosages for oral (chewed or tea) dried and transported Kratom leaf in grams (as sold outside SE Asia).

IMPORTANT NOTE: There are 4 common grades of kratom leaves sold on the commercial market and each is a different potency. Some companies use the terms "Organic Commercial Grade" for the least potent (dosages 5-30 grams dried leaf), "Premium" or "Instant Premium" (dosages 2-15 grams), "Super" (2-8 grams) or "Super Enhanced" (dosages 1-5 grams). Many vendors do not use these labels for their products and the potencies are not standardized in any way. As of 2003, kratom sales usually seemed to include material that fell into the Commercial Grade, but Premium and Super Grade may now be the norm.

Nausea, dysphoria and vomiting are likely with overly strong doses, so it is important for kratom-tea drinkers to start low with the specific leaf material they have and slowly work the dosage up to avoid unpleasant effects.

A teaspoon of dried leaf is usually between 1.5 and 2.0 grams. 1 milliliter of dried leaf is usually between 0.3 and 0.4 grams.

According to a report by the National Drugs and Poisons Schedule Committee of Australia, "Poisindex indicates that in adults, a dose of 50 mg of pure mitragynine has produced motor excitement, rombergism [unsteadiness on feet with eyes closed], giddiness and tremors of the face, extremities and tongue."