Is Cannabis or CBD Safe to Use During Cancer Treatment?

This page is for people in cancer treatment, and their families, who are thinking about cannabis or CBD for symptoms. It covers what the evidence shows, the risks to know, and when to get help.

Cancer treatment can bring nausea, pain, poor appetite, trouble sleeping, and anxiety. Some people wonder whether cannabis or CBD could help.

CBD is short for cannabidiol. It is a compound from the cannabis plant that does not cause a high. This page is about using cannabis or CBD for symptom relief. It is not about cannabis smoke and cancer risk. That is a separate question, covered on our cannabis smoke and cancer risk page.

Two cannabinoid medicines, dronabinol and nabilone, are FDA-approved for nausea and vomiting caused by chemotherapy. Outside that approved use, the evidence is thinner. Some studies suggest cannabis products may help certain people with pain. For appetite, the results have been disappointing. Many studies are small.

The FDA has not approved cannabis or any cannabinoid for cancer symptoms beyond what dronabinol and nabilone cover. In plain terms, there is a real signal of some benefit in some situations. It is not the strong, consistent evidence that exists for many standard symptom treatments.

Cannabis and CBD have not been shown to treat or cure cancer itself. Using them instead of recommended cancer treatment can let the disease progress.

Even when a product is legal, it can affect your cancer medicines. Cannabis and CBD are processed by liver enzymes. Those same enzymes break down many other medicines, including some cancer drugs. Using them together could change how much of a drug stays active in your body. The level could rise to unsafe amounts, or drop enough to make treatment less effective. Our page on CBD, cannabis, and chemotherapy drug interactions covers this in detail. The safest step is simple. Before you start, tell your oncologist and pharmacist about any cannabis or CBD product you use or are considering. Say how often and how much.

Chemotherapy and some other cancer treatments can lower your white blood cell count. That condition is called neutropenia, and it raises your risk of serious infection. Cannabis smoke also contains many of the same harmful chemicals as tobacco smoke and can cause lung problems.

If you are thinking about cannabis for symptom relief while your counts are low, ask your care team before you use anything. Forms that are not smoked, such as oral tinctures and capsules, avoid inhaled plant material. But they are not automatically safe. Doses are hard to judge, and effects last longer. Vaporized products still deliver into the lungs. Inhaling any smoke carries lung risk, whatever your blood counts.

Beyond safety, there is the question of whether you can use these products legally. Cannabis containing THC remains illegal under U.S. federal law. That holds even where states have legalized medical or recreational use. So legality depends on your state. For some workplaces or clinical trials, extra rules apply.

The 2018 Farm Bill removed hemp, meaning cannabis with no more than 0.3 percent THC by dry weight, from the federal definition of marijuana. That is narrower than it sounds. The FDA says it remains illegal to add CBD to food or to label it as a dietary supplement. State laws vary on top of that. Product quality is not consistently regulated either.

If you are considering either, check your state's current rules. Ask your cancer center whether it has its own policy. Some treatment programs and clinical trials restrict use.

Most reactions to cannabis or CBD pass off on their own. A few do not, and two of them matter more during treatment.

• Call 911 or go to an emergency department if you have chest pain or a racing, pounding heartbeat that will not settle. Go too if you become badly confused, frightened or convinced of things that are not real. Do the same if a child or pet has eaten an edible. Do not drive yourself.
• Call your cancer team straight away, at any time of day or night, if your temperature reaches 100.4°F (38°C) or higher during chemotherapy. The CDC calls a fever on chemotherapy a medical emergency, and smoke inhaled while your counts were low is one more way infection gets in. Chills, a new cough or a sore throat alongside it make the call more urgent, not less. If you cannot reach the team fast, go to an emergency department and tell them you are having chemotherapy.
• Call your care team today if you have fallen into rounds of vomiting that keep coming back. Call the same day if you feel faint or are passing little urine after being sick. If you pass out or become confused, call 911.

In long-term heavy users, that vomiting pattern can be cannabinoid hyperemesis syndrome, which can be mistaken for chemotherapy sickness. Tell whoever assesses you that you use cannabis. It changes what they look for.

• CDC — Fever and Cancer Treatment
• MedlinePlus — Dehydration
• StatPearls (NCBI Bookshelf) — Cannabinoid Hyperemesis Syndrome
• National Cancer Institute — Infection and Neutropenia During Cancer Treatment
• National Cancer Institute — Cannabis and Cannabinoids (PDQ), Patient Version
• American Cancer Society — Cannabis and Cancer
• NCCIH — Cannabis (Marijuana) and Cannabinoids: What You Need To Know