Does Weed Affect Plan B?

When taking Plan B, you want to be sure you’re doing everything you can to make it work. That means taking it the right way and avoiding any drugs or medications that may negatively interact with it.

If you smoke marijuana, you may wonder if weed is a no-go after taking a Plan B pill. Does smoking make Plan B less effective? Does it cause health problems? Don’t worry, we’ve got answers!

How Does Plan B Work? 

First, what exactly is Plan B, and how does it work? According to the FDA, Plan B is an emergency contraceptive pill containing 1.5g of levonorgestrel. Levonorgestrel is a synthetic hormone that can stop or delay the release of an egg from the ovary, so Plan B is essentially a larger dose of the hormone in daily birth control.  

To prevent pregnancy, you should take Plan B as soon as possible within 72 hours after unprotected sex. Planned Parenthood explains that when taken within this time frame, Plan B can lower your chance of getting pregnant by 75-89%.  

It is important to remember that Plan B does not do anything to treat or prevent sexually transmitted infections (STIs) or sexually transmitted diseases (STDs). If you have had unprotected sex and STIs or STDs may be a concern, it is best to get tested and speak to your doctor.

Side Effects of Plan B

Like many drugs and medications, Plan B can cause temporary side effects. The most common include irregular periods, headache, fatigue, nausea, and dizziness.

Everyone is different, and the side effects experienced can vary from person to person. If you’re unsure or concerned about any side effects that you experience, contact a doctor.   

Does Cannabis Alter Plan B’s Effectiveness?

So, you’re taking Plan B correctly and are aware of the side effects. Can you still smoke? 

No need to fear! Thankfully, there has been no evidence found that weed decreases the effectiveness of Plan B. You can smoke marijuana before or after taking Plan B with no impact on the effectiveness of your birth control. 

Other Interactions Between Cannabis and Birth Control

Although there has been a decisive lack of evidence suggesting that cannabis can stop Plan B from working, you may still find some advice not to use both at the same time for other reasons. 

This is largely because of health concerns surrounding the interacting side effects of cannabis and birth control. Specifically, some findings have suggested that cannabis impacts blood pressure. There are also findings proposing that birth control can impact blood pressure and increase the risk of blood clots. 

Therefore, because of the combined overlapping side effects of cannabis and birth control, some postulate about health concerns that could emerge. 

However, these conversations are largely centered around birth control that is taken regularly, not Plan B, which is taken on an occasional, as-needed basis. Furthermore, these health concerns are still unrelated to the effectiveness aspect of birth control. 

What About Other Drugs?

Although cannabis does not decrease the effectiveness of Plan B, other medications might. These include:

• The antibiotic Rifampin (though other antibiotics do not reduce effectiveness)
• The antifungal Griseofulvin (though other antifungals do not reduce effectiveness)
• Certain HIV medicines
• Certain anti-seizure medicines (these are also sometimes used to treat disorders like bipolar)
• St. John’s Wort (an herb)

If you are wondering about how another supplement, drug, or medication may interact with your birth control, it’s always a good idea to ask your doctor for more advice. 

Final Takeaways

If you’ve been worried about your weed consumption lowering the effectiveness of your Plan B, you can rest easy. Although some have speculated about the health impacts of smoking while on Plan B, there has been no evidence found suggesting that Plan B’s effectiveness is directly impacted by cannabis. 

Of course, if you are taking Plan B, it is important to follow the directions and take it as intended (within 3 days after unprotected sex) whether you are smoking or not. Additionally, if you have questions or concerns about Plan B and how to take it effectively or how other medications or supplements that you take may interact with it, it is always advisable to consult your physician.