The manufacturer will probably give you a recommended dosage, but bear in mind that this isn’t set in stone. What you need to find is your own minimum effective dose. “Minimum effective dose” is a medical term which refers to the amount of a substance you need for the results you want, and above which, the substance doesn’t increase in effectiveness.
When looking at isolate, it is important to verify the purity. While many are in the 99.9+% range with no identifiable amounts of THC, there are lower purity ones (such as 99.5% or lower) that may still have trace amounts that show up on the labs. This small amount is typically negligible, and is nowhere near the amount usually found in Full Spectrum products. But it’s still something to be aware of for those seeking the purest they can find.
The aforementioned entourage effect is the main reason behind the efficacy of whole plant extracts. There are over 100 ‘identified’ compounds in the cannabis plant. While most of these compounds have their own therapeutic benefit, they combine synergistically to provide a far better performance than any single compound, including CBD. Here are a couple of examples of conditions that benefit from the entourage effect: