CBD is well tolerated in humans with doses up to 600 mg not resulting in psychotic symptoms (15). In the few small placebo-controlled studies performed, no significant CNS effects were noted. Oral CBD undergoes extensive first-pass metabolism via CYP3A4, with a bioavailability of 6%. Following single doses in humans, the half-life of CBD when taken orally is about 1 to 2 days.1 In vitro studies have shown that CBD is a potent inhibitor of multiple CYP isozymes, including CYP 2C and CYP3A (16, 17). Whether these in vitro observations are relevant at plasma concentrations likely to be seen in patients is unclear. In addition, given its metabolism via CYP3A4, clinical trials of CBD in patients receiving enzyme-inducing AEDs, such as carbamazepine or phenytoin, will require detailed pharmacokinetic studies.
Pharmacology published a study in 2016 looking at medical marijuana for migraines, specifically in relation to its effects on serotonin, with very positive results. You’ll notice that neither study looked at CBD in isolation from other cannabinoids (which is an issue with a lot of research on CBD and pain). Truthfully, the research on CBD alone just isn’t sufficient to make any pronouncements about its effects on headache pain.
The amount of milligrams of CBD you should take depends on your specific reason for taking CBD. If you are using CBD to treat chronic pain, you might take a much higher dose than someone who would be using CBD for general wellness reasons. Google search for your specific condition or reason for taking CBD to find the dose that is appropriate for you. You can take CBD in high qualities, so feel free to test out different dosages and see how your body reacts. A standard dose of CBD is 10 mg once a day, but this varies so widely because each individual is different so this can’t be taken as a recommendation for you.