There is no officially established waiting period between taking CBD and Ativan (lorazepam). No clinical guideline specifies a safe number of hours to separate the two. The reason this matters, though, is that CBD can increase how much lorazepam builds up in your system by slowing down the enzyme your body uses to break it down. Understanding how that interaction works helps you gauge the real risk.
Why CBD and Ativan Interact
Lorazepam is unusual among benzodiazepines. Most drugs in its class are broken down by the liver’s CYP450 enzyme system, but lorazepam skips that step almost entirely. Instead, your body clears it through a process called glucuronidation, primarily using an enzyme called UGT2B15, with contributions from UGT2B7 and UGT2B4. This is actually why lorazepam is often considered a “safer” choice for people on multiple medications.
CBD, however, inhibits UGT2B7 activity. That means CBD can slow the rate at which your body eliminates lorazepam, causing lorazepam levels in your blood to rise higher or last longer than they normally would. On top of that, CBD is a potent inhibitor of several CYP450 enzymes (CYP2C9, CYP2C19, CYP3A4, and CYP1A2), which could affect other medications you take alongside either substance.
The practical result: taking CBD and Ativan close together can intensify sedation, slow your reaction time, impair your judgment, and in some cases depress your breathing. The FDA has specifically warned that using CBD with drugs that slow brain activity, including those for anxiety and sleep, increases the risk of excessive drowsiness and injury.
How Long Each Substance Stays Active
After a single oral dose, CBD has a half-life of roughly 1 to 3 hours. That means most of the CBD from a one-time dose clears within about 6 to 15 hours. However, if you take CBD daily, the picture changes dramatically: chronic use extends CBD’s half-life to 2 to 5 days, because CBD accumulates in body fat and releases slowly over time. A regular CBD user still has meaningful levels of CBD in their system even a day or two after their last dose.
Lorazepam has a plasma half-life of about 12 hours, with its main breakdown product lingering for around 18 hours. A general rule of thumb is that it takes about five half-lives to fully clear a drug, which puts lorazepam’s total clearance time at roughly 60 hours (about 2.5 days).
This is the core problem with trying to “time” the two apart. If you use CBD regularly, it doesn’t fully leave your system between doses. And the enzyme inhibition CBD causes isn’t like flipping a switch. It’s a time-dependent process for some enzymes, meaning CBD’s effect on drug metabolism can linger even after CBD levels drop.
Does CBD Dose Matter?
Yes, significantly. CBD’s ability to interfere with drug metabolism is dose-dependent and nonlinear, meaning the effect doesn’t scale in a simple, predictable way. Animal research has shown that lower doses of CBD (equivalent to roughly 1 mg/kg of body weight) did not meaningfully inhibit enzyme activity, while doses of 10 mg/kg and above clearly did. The threshold for significant enzyme inhibition appears to fall somewhere in that range.
For context, many over-the-counter CBD products deliver 10 to 50 mg per dose, which is on the lower end. Prescription CBD (Epidiolex) is dosed far higher, sometimes reaching several hundred milligrams per day. The higher your CBD dose, the more likely it is to interfere with lorazepam clearance, and the more cautious you should be about timing.
A Practical Approach to Timing
Since no clinical trial has tested specific timing intervals between CBD and lorazepam, any recommendation is an educated estimate based on pharmacokinetics rather than direct evidence. Here’s what the available data suggests:
- Occasional CBD use at low doses (under 25 mg): Waiting at least 4 to 6 hours after taking CBD before using Ativan allows most of a single CBD dose to clear. The interaction risk at these doses is lower, but not zero.
- Regular CBD use or higher doses (50 mg and up): CBD accumulates in your body with daily use, and its half-life extends to days rather than hours. Spacing doses by a few hours offers limited protection because CBD is still present in your system. The interaction is essentially continuous.
- Prescription-strength CBD (Epidiolex): At therapeutic doses of 5 to 20 mg/kg per day, the enzyme inhibition is substantial and persistent. Your prescriber should be adjusting your lorazepam dose accordingly rather than relying on timing alone.
The honest answer is that if you take CBD daily, no waiting period fully eliminates the interaction. Separating doses by several hours may reduce peak overlap, where both substances hit their highest blood levels at the same time, but it won’t prevent CBD from affecting how your body processes lorazepam.
What the Interaction Feels Like
When CBD amplifies lorazepam’s effects, you may notice stronger-than-expected drowsiness, unusual difficulty concentrating, impaired coordination, or a “heavy” feeling that lasts longer than your normal response to Ativan. Elderly adults and people with liver problems are especially susceptible because both clearance pathways already work more slowly in these groups.
The combination doesn’t just make you sleepier. It can impair your ability to recognize how impaired you are. That’s the specific concern behind the FDA’s warning about injuries: people combining these substances may feel capable of driving or operating equipment when they’re not.
What Actually Helps Reduce Risk
Rather than relying solely on timing, there are more reliable ways to lower your risk. If you’re already taking Ativan and want to add CBD (or vice versa), starting with the lowest possible CBD dose lets you observe how your body responds before increasing. Paying attention to how sedated you feel in the first few days of overlap gives you a practical signal. If you notice unusual drowsiness or coordination problems, that’s the interaction showing up.
Keeping your prescriber informed that you use CBD is the single most useful step. They can adjust your lorazepam dose downward to account for the slower clearance. This is, in fact, the recommendation from published interaction reviews: consider reducing the dose of lorazepam when it’s used alongside a UGT2B7 inhibitor like CBD, rather than trying to time your way around the interaction.