In reminiscing about your high school chemistry class, you may remember hearing a certain term: “half-life.” That’s the time it takes for an element to deteriorate to half of its original amount. Just as radioactive elements have half-lives, so do chemicals – including drugs and supplements, which deteriorate inside the body at different rates depending on several factors. This is known as “biological half-life,” and it’s useful in medical and pharmacological applications to determine the quantity and frequency of dosage of a particular drug.
As you might expect, CBD has a half-life as well – though it varies depending on the method of consumption. A 2012 study found that oral administration of CBD resulted in a half-life of two to five days, in contrast to 18 to 33 hours when taken intravenously and 27 to 35 hours when smoked. A separate study from 2014 concluded the half-life of orally-administered CBD to be around one to two days.
How Long Does CBD Stay in Your System After Taking It?
So, how many half-lives does it take for CBD to fully dissipate?
As a general rule in pharmacokinetics (the study of how drugs move throughout the body), a substance will deteriorate almost completely within four to five half-lives, as broken down below:
- 1 half-life: 50%
- 2 half-lives: 25%
- 3 half-lives: 12.5%
- 4 half-lives: 6.25%
- 5 half-lives: 3.125%
Taking this into account, with the assumption that the half-life of CBD, when taken orally, is about one to two days, we can effectively say that it would take four to five times that amount (four to ten days) for a single dose of CBD to be eliminated by roughly 97 percent, at which point it approaches undetectable levels. This measurement is supported by research.
Scientists in a 1991 study at the University of Arizona College of Pharmacy orally administered a healthy dose of 700mg of CBD to 14 patients every day for six weeks and found that levels were virtually undetectable after one week of discontinued use.
Although its half-life plays a pivotal role in determining how long CBD stays in your system, it is only a baseline; many other factors contribute to the process, including body weight, age, lifestyle, metabolism, and frequency and quantity of dosage. CBD is fat-soluble, meaning it is stored in fat cells. It, therefore, stands to reason that an overweight person of considerable age will metabolize CBD at a lower rate than someone who is young and active. Likewise, someone taking 100mg doses of CBD twice a day will maintain much higher levels over a longer period of time than someone taking 25mg every other day.
Truthfully, there’s no definitive answer to how long CBD will linger in the body. There are simply too many varying factors to consider. The question itself may be born out of curiosity for some, but for many others, it may be asked out of fear of failing a marijuana drug test. Given that CBD is now federally legal with a THC percentage cap of 0.3 percent, there is little likelihood that this could happen.
CBD’s duration in the body is just one of the many inquiries that scientists are exploring. As the popularity of CBD products rises steadily, continued research will reveal additional insight into the mysteries that are yet to be discovered.