Medical marijuana


Cannabis, a plant also known as marijuana, is commonly known for its recreational use. Because of the impact it has on human behavior, its use is federally illegal in the United States. However, many states have adopted legislation enabling what is called medical use or adult use, or both. But marijuana has chemicals, called cannabinoids, that have shown promise in helping ease breast cancer treatment side effects such as nausea, vomiting, and pain.


What is medical marijuana?

Medical marijuana is a phrase used to describe the use of the cannabis plant, either the whole plant or its chemical extracts, to treat symptoms of certain medical conditions or treatment side effects. The marijuana plant contains cannabinoids, unique chemicals that have been found to have medical benefits such as relieving nausea, pain, and loss of appetite that may be side effects of breast cancer treatment.

Delta-9-tetrahydrocannabinol, commonly called THC, is the most-studied cannabinoid compound. But it is also the chemical that produces the intoxicating effect that draws people who use marijuana for recreation. Another cannabinoid, called cannabidiol or CBD, has also shown some health benefits without making you feel intoxicated, or high. Producers have bred marijuana plants that have higher levels of either THC or CBD to achieve certain effects, but there may be added benefits when both are present in the plant.

Scientists have been able to extract or replicate cannabinoids to get a specific effect in a pill or liquid form. Two medicines based on THC, dronabinol (Marinol or Syndros) and nabilone (Cesamet), have been approved by the Food and Drug Administration (FDA) to ease nausea and vomiting caused by cancer chemotherapy.


How medical marijuana is taken

There are several ways to take medical marijuana, including many of the same methods used to take marijuana recreationally. Dronabinol and nabilone, synthetic versions of THC, have been approved by the FDA to treat nausea and vomiting caused by cancer treatments. THC is an active chemical in marijuana that has shown health benefits but also has side effects such as lightheadedness, dizziness, trouble concentrating, and feeling high — effects that are also present in these synthetic pills.

Dronabinol and nabilone are treated the same as other medicines: they can be prescribed by your doctor and may be covered by private insurance and government programs such as Medicare and Medicaid.

  • Dronabinol is a synthetic version of THC available as a pill or liquid taken by mouth. It is approved to treat nausea, vomiting and loss of appetite. During a chemotherapy cycle you may take four to six doses in a day for nausea, one every 2 to 4 hours. A first dose is taken an hour or more before getting treatment. For appetite, two doses a day is recommended, one each before lunch and dinner.
  • Nabilone is a synthetic version of THC available as a pill taken two to three times a day for nausea during treatment with chemotherapy. A first dose is taken 1 to 3 hours before chemotherapy and it may be continued for 48 hours after chemotherapy.

Federal law still prohibits other ways people take or use medical marijuana, including any methods that burn or heat the dried marijuana plant to inhale smoke or vapor. These methods also are not FDA approved for use in side effect management.

But many states permit people with medical conditions such as breast cancer to buy and use medical marijuana in some or all of these forms:

  • Smoking involves burning marijuana in a rolled cigarette, a glass pipe, a water pipe (a pipe in which the smoke is passed through water before being inhaled), certain kinds of vaporizers, or another device and inhaling the smoke.
  • Edibles are items containing medical marijuana that can be swallowed or put under the tongue. Edibles deliver medical marijuana’s effects when eaten. Well-known examples of edible marijuana products include baked goods and gummies or chews, but many others have become available in recent years including drinks, lozenges, oils, tinctures, and powders that can be used in a range of food and drink products.
  • Vaporizers and e-cigarettes heat an oil extract without burning it. The result is a vapor that can be inhaled.
  • Topical creams or gels can be applied to the skin.
  • Patches deliver medical marijuana through the skin.

Each method comes with its own pros and cons:

  • With a cigarette or pipe, much of the smoke dissipates when you are not inhaling it. Smoking can also be hard for people with lung problems. When marijuana is smoked, you feel its effects very quickly.
  • Vaporizers and e-cigarettes come with the same benefits as smoking and may be more convenient. Some evidence suggests vaping may affect the lungs less than smoking, but there is limited information on the safety of many ingredients in vaping oils.
  • Edibles and pills can be difficult to take when you are experiencing nausea. They can also take longer to go into effect. Edibles may be easier on your lungs, allow you to control the dose more carefully, and can be used more privately than smoking.

As many states permit medical and recreational use of marijuana, many new marijuana products have become available, especially in edible form. Ask your healthcare team about safe products that can suit your needs.

Remember that each state approves marijuana use differently. They control which health conditions qualify for medical marijuana in your state, in what forms you can buy it, and how you get approved to use it. Cancer is among the conditions permitted in most states.

Dosing for medical marijuana is less regulated than with most medicines. The right dose can be very different from person to person. The common advice is to start with a small amount or dose at first and then try more if your symptoms or side effects don’t get better, increasing the amount a little at a time. If you are not getting relief, ask your doctor about other ways to take medical marijuana or marijuana with different levels of THC and CBD.

No matter what you choose, you should always speak with your healthcare team about any new activity or substance that may affect your treatment.


How medical marijuana works

The body makes chemicals similar to those found in marijuana. These chemicals made in your body are called endocannabinoids, and there are two types of special receptors for them in the brain and throughout the body.

THC and CBD, different cannabinoids found in various forms of medical marijuana, can bind to these receptors and ease some of the side effects associated with breast cancer treatment. Both THC and CBD bind to both types of receptors. THC binds more strongly to a type of receptor found mainly in the brain, and in lesser amounts in other areas of the body. CBD binds to another group of receptors found mainly in parts of the body that have immune function including certain blood cells, the spleen, and the tonsils.

When cannabinoids such as THC or CBD bind to these receptors, they can ease treatment side effects such as nausea and vomiting.


Who gets medical marijuana?

Medical marijuana may be available for people who are having an especially difficult time with treatment side effects that don’t get better with other medicines or management techniques.

Because of the impact marijuana has on human behavior, it has been illegal in the United States since the early 20th century. But individual states have recently started changing their laws to allow people with conditions such as breast cancer to use marijuana for medical purposes.

The National Conference of State Legislatures keeps a list of which states allow medical marijuana use. Even if your state is on the list, there are likely additional steps you must take to use it legally, such as having a doctor certify your condition and registering with the state. Each state has its own rules about what medical marijuana products are allowed and the steps you must take to get and use it legally. For more information, see States that allow medical marijuana below.


Insurance coverage for medical marijuana

Neither government health programs, such as Medicaid and Medicare, nor private health insurance cover medical marijuana. Two FDA-approved medicines based on THC, dronabinol and nabilone, however, may be covered by insurance plans.


Side effects

Like any medicine, medical marijuana can come with some side effects, including:

  • Rapid heartbeat
  • Low blood pressure
  • Bloodshot eyes
  • Muscle relaxation
  • Slowed digestion
  • Dizziness
  • Depression
  • Paranoia
  • Hallucinations

Smoked marijuana may have some of the same effects on the lungs as smoking tobacco. Stopping marijuana use may cause sleeplessness, irritability and hot flashes. Marijuana is less addictive than many prescription medicines and has a much lower risk of overdose.


Drug interactions with medical marijuana

The federal ban on medical marijuana has made it a challenge to study its effects and potential interactions with other medicines. Research observing the effects of cannabinoids on enzymes and processes in the body suggest that it could interfere with many different medicines, including trastuzumab (Herceptin and biosimilars) for breast cancer. At least one study has found an association between cannabis use and shorter survival in people taking immunotherapy for other cancers, though that study also had significant limitations.

It’s important to speak to your doctor about any potential interactions with treatment before starting medical marijuana. Your doctor should also be aware of any other prescriptions, over-the-counter medicines, supplements, or herbs you are taking to be able to assess possible risks. Prescription labels for synthetic THC-based medicines dronabinol and nabilone include several medicines that are of particular importance to mention including antidepressants, antihistamines, different forms of pain medicine, and sleeping pills, among others.


Medical marijuana & federal law

Many states have changed their laws to allow people to use marijuana for certain medical conditions or treatment side effects. But the federal government still considers marijuana a Schedule 1 substance. This category is used to strictly control substances considered to have a high risk for abuse and no currently accepted medical use. This category puts strong restrictions on who can legally grow, buy, or use marijuana whether for recreation, treatment, or research. These federal restrictions conflict with the laws of individual states. This disagreement between state and federal law can make it difficult to know what is allowed.

The federal government has not enforced its restrictions against people who obey their state’s laws but does restrict researchers seeking to learn more about its possible uses in breast cancer treatment. There is much to learn about the effects of medical marijuana and how it can be used to help people with medical conditions, but the Schedule 1 classification makes research more difficult. The status comes with strict rules for using marijuana in a study and makes it harder to get the funding needed to hold clinical trials.

If you are considering medical marijuana to help ease breast cancer treatment side effects, check your state’s laws about its use and speak with your doctor about if it would be right for you.

The difference between state and federal policy on marijuana makes it hard to predict the future of any medical marijuana program. Aside from dronabinol and nabilone, which are approved by the FDA, doctors cannot prescribe medical marijuana because of federal law. Because of this, they can only tell you their opinion on whether it might work for you — but they can’t tell you to take it. It’s also possible that your doctors may not bring up medical marijuana, so you may have to start the conversation if you’re interested.

Because doctors can’t give you a prescription for medical marijuana as they would with other medicines, many states require instead that a doctor certify that you have a condition that qualifies for medical marijuana use. How they certify depends on the state. Your state may require a written letter from your doctor or that they fill out an online form. In some states, the doctor must also register in order to issue medical marijuana eligibility. If your doctor is not registered, they may be able to refer you to someone who is.


States that allow medical marijuana

The National Conference of State Legislatures tracks which states have passed laws to permit the use of medical marijuana. As of April 2023, 38 states as well as Washington, D.C. have programs allowing for the regulated use of medical marijuana products. Some states, such as Colorado and Washington, have legalized marijuana even for recreational use. But in other states, there may be strict regulations on how you get medical marijuana and in what forms it is permitted.

An additional nine states have loosened their laws somewhat. Some allow medical marijuana that is bred to have lower amounts of THC, usually with higher amounts of CBD. Though CBD has been shown effective in treating some conditions, such as seizures, it may not be as effective at treating breast cancer treatment side effects. Other states allow people arrested for marijuana use to claim medical need as a defense in court, but do not have a system to allow you to use marijuana legally.

Map of the United States showing which states allow medical marijuana use or allow medical use as a legal defense, and where all marijuana use is illegal.

States with programs allowing regulated use of medical marijuana (as of April 2023) include Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, Florida, Hawaii, Illinois, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Dakota, Oklahoma, Ohio, Oregon, Pennsylvania, Rhode Island, South Dakota, Utah, Vermont, Virginia, Washington (state), and West Virginia.

States that allow people arrested for marijuana use to claim medical need as a defense in court, but do not have a system to allow legal use of marijuana (as of April 2023) include Georgia, Indiana, Iowa, North Carolina, South Carolina, Tennessee, Texas, Wisconsin, and Wyoming.

No matter what, obey all local laws and do not travel with medical marijuana to avoid carrying it into a state or locality that bans it.


Medical marijuana & the workplace

You can be legally comfortable using medical marijuana so long as you obey the rules of your state and you are listening to the advice of your doctor. But be aware that there are some other impacts outside the law, such as your workplace. If you are working, check your employer’s policy on medical marijuana use. Several states protect employees taking medical marijuana, so you may be able to request a reasonable accommodation in those places. Reasonable accommodations are changes made in your job, workplace, or schedule to help you work more comfortably while living with a medical condition or its side effects. These are supported by the Americans With Disabilities Act, or ADA.

In most states it is up to your employer to determine their policy on marijuana use. Some types of jobs may not allow its use at all. For example, you may not be protected if you work for the federal government, or if there is a safety concern, such as jobs that require driving or operating heavy machinery.


Reviewed and updated: June 14, 2023

Reviewed by: Brooke Worster, MD, FACP


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