Common side effects
You're unlikely to get any side effects from Pepto-Bismol if you follow the instructions for taking it.
One common side effect is your poo or your tongue turning black. This is harmless.
This happens when bismuth (the active ingredient in this medicine) comes into contact with small amounts of sulphur in your saliva and digestive system. They combine to form bismuth sulfide, a black substance. As it slowly makes its way out of your body you may see black poo.
This side effect usually goes away when you stop taking the medicine but it may take several days.
If your tongue or your poo is still black after you've stopped taking Pepto-Bismol for several days, speak to your doctor or a pharmacist.
Tell your doctor or a pharmacist if you have any other side effects that bother you or do not go away.
Serious allergic reaction
In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to Pepto-Bismol.
Immediate action required: Call 999 now if:
- your lips, mouth, throat or tongue suddenly become swollen
- you're breathing very fast or struggling to breathe (you may become very wheezy or feel like you're choking or gasping for air)
- your throat feels tight or you're struggling to swallow
- your skin, tongue or lips turn blue, grey or pale (if you have black or brown skin, this may be easier to see on the palms of your hands or soles of your feet)
- you suddenly become very confused, drowsy or dizzy
- someone faints and cannot be woken up
- a child is limp, floppy or not responding like they normally do (their head may fall to the side, backwards or forwards, or they may find it difficult to lift their head or focus on your face)
You or the person who's unwell may also have a rash that's swollen, raised, itchy, blistered or peeling.
These can be signs of a serious allergic reaction and may need immediate treatment in hospital.
Other side effects
These are not all the side effects of Pepto-Bismol. For a full list see the leaflet inside your medicines packet.
You can report any suspected side effect using the Yellow Card safety scheme.