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Why is my psychiatrist asking for a blood test?

Dear Alice,

I recently went to a new psychiatrist and he requested a blood test. I was wondering what he was ordering a blood test for, so I asked him and he said many things. I was wondering if he is testing me for drugs? I am not a huge smoker (marijuana). But I do smoke usually multiple times a week, and did not feel the need to share that with my doctor yet. Could you tell me what they are testing me for?

Dear Reader, 

It’s reasonable for you to ask health care providers, including mental health professionals, questions if you want more information about your care. In this case, there are a few different things that your psychiatrist might be testing for. While it’s ultimately up to you whether you want to talk to your psychiatrist about your marijuana (also known by the names weed, pot, etc.) use, you might consider doing so to help guide your own mental health treatment. Read on for more information about blood tests in psychiatric settings, marijuana use and blood tests, and marijuana use coming up during therapy. 

Technically your psychiatrist's right—there are many things he could be testing! In fact, there are too many to list in this response. However, if you have a mental health diagnosis or are taking medication, consider checking out which lab tests are associated with different diagnoses and medications for more information. In general, psychiatrists tend to order blood work for a few reasons. Sometimes symptoms of certain mental illnesses are actually symptoms of underlying physical distress in disguise. Blood tests can be helpful when your psychiatrist's making a mental health diagnosis by ruling out pre-existing physical disorders. Finding out you have an existing physical disorder might also influence which medications are safe to take. Blood tests can also be helpful in monitoring any medications you might be taking currently or in the future. Certain psychiatric medications may have side effects. Routine blood work can help your doctor see if you're experiencing any complications. 

Although recreational drug use doesn’t fall under these categories, psychiatrists may still conduct testing as part of their clinical practice if indicated. If you haven’t raised any concerns about marijuana use interfering with your mental health, it's unlikely your psychiatrist will test for it. Additionally, drug testing for marijuana via bloodwork is much less common than urine testing because the active drug component in marijuana, THC, doesn’t stay in the bloodstream as long after use as it does in urine. 

That said, if you don’t want your psychiatrist to know about your marijuana use yet and would rather play it safe, it might be helpful to ask him if you can refuse the blood test. You might also ask about what the consequences might be for doing so. Setting boundaries about what you want out of therapy can be a helpful way to make sure you feel safe and build trust between you and your psychiatrist. 

You might also want to reflect on why you don’t feel comfortable sharing this information with your psychiatrist. Do you feel uncomfortable with him in general? Would you feel more comfortable sharing this with a different mental health provider? If this is the case, you might consider finding a different psychiatrist with whom you feel more confident in confiding your marijuana use. Are you concerned that others might find out about your drug use? If so, it might be helpful to know that while there are certain exceptions—such as disclosures of child abuse or threats to your own or others’ safety—psychiatrists are required to keep much of a patient’s information, such as drug use, confidential. Learning more about how to find a new mental health professional and ensure privacy in a therapeutic context might help you clarify your discomfort in sharing this information with your current psychiatrist. 

Even though it seems you’re not comfortable talking about it now, there are some reasons you might want to open up to your psychiatrist about your recreational drug use at some point. For one thing, your psychiatrist will be better equipped to help treat you if he has as much information as possible about your habits and behaviors. There are some medications (for both mental and physical health) that may have negative and potentially dangerous interactions with marijuana. If your psychiatrist knows about your weed use, he can avoid prescribing you those medications to keep you safe from potentially adverse drug interactions. 

Additionally, your psychiatrist can provide guidance about whether marijuana use is helpful or harmful to your mental health care. Some people include marijuana in their routine and find it helpful, while for others, they may find it less helpful. 

For more information about how marijuana and therapy intersect consider checking out the Go Ask Alice! archives for resources about the long-term effects of marijuana use, the process of finding a therapist, and privacy in therapy. Best of luck with deciding whether to pass on telling your psychiatrist about your marijuana use.

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Last updated Jan 19, 2024
Originally published Nov 14, 2014