The side effects of medical cannabis will vary depending on: The amount of medical cannabis you use How often you take your medical cannabis How you take your medical cannabis You’re more likely to get side effects from medical cannabis if you: Take a high dose Use a vaporiser Use it very often Around 1 in 10 people get side effects from medical cannabis such as: Feeling drowsy, sleepy or tired Being less hungry than usual A high temperature or fever Vomiting, nausea (feeling sick) or diarrhea Around 1 in 100 people might get these side effects after using medical cannabis: Feeling faint A change in blood pressure A change in how fast your heart is beating Tummy pain Mouth or teeth changing colour Dry mouth You should not drive if you feel drowsy or your vision becomes blurry. You should not drink alcohol if you’re using medical cannabis. If you’re pregnant, breastfeeding or trying for a baby, you should not use medical cannabis. Although rare, you may have an allergic reaction to medical cannabis. If this happens to you, stop taking medical cannabis and call 999. The general signs of an allergic reaction include: Swollen face, lips, mouth or tongue Hives, or a bumpy red rash on your skin Itchy skin Breathing difficulties or wheezing If you get side effects or have any concerns, you should speak to the doctor that is prescribing medical cannabis for you. You can also report side effects to the MHRA yellow card scheme or report this to the Pharmacy so that a report can be made on your behalf.