To be clear, there is no one specific test, scan, or anything else of the sort that you can do to determine whether or not you need CBD oil for pain. Also, since cannabis is not yet recognized by the FDA, you unfortunately can’t really go to your doctor either and have them recommend it; until marijuana is FDA-approved, it cannot be prescribed by physicians.
The human body has an endocannabinoid system — a natural system that maintains homeostasis or balance, in the body. The endocannabinoid system has CB1 and CB2 receptors. These are found throughout the body. CB1 receptors are generally located in the central and peripheral nervous system and CB2 receptors are generally found in the brain, immune system, and gastrointestinal system. CBD binds to these receptors creating changes and effects in the body
The most commonly used form of CBD is CBD oil. Combining CBD extract with a carrier oil like coconut oil, it can be ingested or vaped, bringing a lot of variety. But because marijuana legalization is in such a murky situation with both federal and state laws to grapple with, CBD oil's legality can be hard to parse depending on where you are. Let's start with legality at the federal level.
You can thin the CBD with terpenes, encapsulate it in dextrin, drive the terpenes off with heat, and use the now water-soluble CBD in water with an ultrasonic fogger/oil-diffuser. It won’t precipitate, but the level of solubility is pretty low even with encapsulation, think 100mg per 200ml. The evaporation rate of those units is somewhere like 50ml/hour, which works out to .83mg of CBD being vaporized a minute, or .14mg every 10 seconds. That’s a miniscule rate.
Dry Mouth: As is the case with many other hemp- and marijuana-based products, CBD oil often leads to a condition known as dry mouth (or cottonmouth). This is likely due to cannabinoids altering receptors in the lower jaw that trigger salivation. In most cases, mild discomfort and stronger-than-average thirst are the only issues associated with dry mouth.
Outside of those four states, consumers must put their trust in the manufacturer. Sometimes that’s warranted, and sometimes it’s not. In 2016 and 2016, the FDA ran tests on several CBD products and found that many of the products had far less CBD than advertised, and in some cases none at all. You can find those test results here for 2015, and here for 2016. (These FDA tests were done as a one-off project. CBD products are not approved by the FDA for the prevention, mitigation, or treatment of any disease or condition.)