The biological limit for the percentage of THC is 35%, so it is possible to find flowers with a THC content above 25%. While it is rare to find flowers with a THC content higher than 25%, it is much more common to see claims of THC levels between 25 and 30%. Generally, the best quality cannabis you'll find will have a THC content between 25 and 30%. Anything above 20% should be considered very strong.
Contrary to popular belief, the percentage of THC has nothing to do with the quality of the herb or its potency. In fact, since THC interacts differently from person to person, a strain with a high percentage may be “better” for you than others. So how much is too much THC and what do the percentages actually mean for your expectation? The truth is that there is no research to indicate that any level of THC is beneficial for any medical condition. In fact, research conducted by the University of Colorado and published in JAMA Psychiatry found that THC content is also a poor indicator of potency.
Microdosing, or consuming small amounts of cannabis, is ideal for consumers who want to avoid poisoning associated with THC and, at the same time, benefit from the relief offered by cannabis. Ideally, microdosing should involve consuming less than 10% THC, as there is no good research on concentrations higher than this for any medical condition and there is significant literature on the negative effects of high-potency THC. It's also important to note that there may be notable differences in the levels of THC in different cannabis products. For example, hashish from Dutch coffee shops may have an average THC content higher than flowers.
Additionally, a study on prenatal cannabis exposure in rats found that rats exposed to THC showed a shorter latency until the first active lever pressure to obtain heroin and sought more heroin during mild stress and drug extinction than animals not exposed to THC. In general, if you're looking for an extraordinary experience, the strain with the highest percentage of THC is a good starting point. However, it's important to remember that there is no research to indicate that this level of THC is beneficial for any medical condition. For experienced cannabis users, the effects of consuming a large amount of a very potent and THC-rich strain may be a bit disorienting, but they are nonetheless delightfully pleasing.