The pick
A CBD tincture, 10 to 25 mg per dose, held under the tongue. CBD has weak CB1 activity and no THC high, so doses do not stack into a psychoactive effect. Onset runs 15 to 45 minutes. Felt effects run 2 to 4 hours.
If the goal is a long effect window, the pick changes. See the options below.
Half-life in one sentence
Half-life is the time plasma concentration takes to fall by half. It is not the same as the time a dose feels active.
THC half-life
- Terminal plasma half-life: 20 to 30 hours in infrequent users.
- Terminal plasma half-life: 3 to 13 days in chronic heavy users.
- THC is fat soluble. It leaves blood, enters fat, and returns to blood over days.
- THC-COOH, the main metabolite, clears slower than THC. Urine screens detect it for about 3 days after one dose and up to 30 days in heavy users.
CBD half-life
- Terminal plasma half-life at steady state: 56 to 61 hours. This figure comes from the FDA label for Epidiolex, an oral CBD solution.
- Single-dose values run shorter than the steady-state figure.
- Oral bioavailability: about 6 percent. Most of an oral dose is lost in the gut wall and liver.
- CBD binds CB1 and CB2 receptors with low affinity. It does not produce the THC high.
Side by side
- THC: 20 to 30 hours plasma half-life, 1 to 3 hours of effect from smoked flower.
- CBD: 56 to 61 hours plasma half-life at steady state, 2 to 6 hours of effect from a tincture.
- THC: stored in fat, detected for days to weeks.
- CBD: limited fat storage, detected for days.
Why the numbers differ
Body fat, liver enzymes, dose, route, and frequency of use change both numbers. A person with more body fat stores more THC and clears it slower. Repeat CBD doses extend the half-life past single-dose values.
Cannabis Metabolite Half-Life: How Long THC Really Stays in the Body
CBD inhibits CYP2C19 and CYP3A4 in lab studies. It raises blood levels of clobazam and other drugs that use those enzymes. Ask a pharmacist before adding CBD to a prescription routine.
Options
1. CBD tincture, 10 to 25 mg
Sublingual oil. Onset 15 to 45 minutes. Effect window 2 to 6 hours. No high. Good starting point for daytime use.
2. THC edible, 2.5 to 10 mg
Onset 30 to 120 minutes. Peak at 2 to 4 hours. Effect window 6 to 8 hours. Liver conversion to 11-hydroxy-THC makes the effect stronger than inhaled THC at the same dose.
3. THC flower or vape
Onset 1 to 10 minutes. Effect window 1 to 3 hours. Blood THC peaks in minutes and drops fast, but THC-COOH remains for days.
4. 1:1 CBD to THC tincture
Equal parts. Effect window 4 to 8 hours. CBD does not block the THC high, but it can change how the dose feels for some users.
What half-life does not tell you
Half-life does not predict the strength of a high, the onset time, or the result of a urine screen. Those depend on dose, route, body fat, and frequency of use. A single 10 mg edible and a 10 mg daily edible habit produce different clearance curves.
Bottom line
CBD holds the longer plasma half-life at steady state. THC holds the longer detection window because of fat storage and the THC-COOH metabolite. Match the format to the window you want: tincture for a short CBD window, edible for a long THC window, flower for a short THC window.