A side effect is any effect of a medicine other than the one you are taking it for. Most are mild and settle within a couple of weeks. A few are important and need to be reported quickly.
Side effects happen because medicines rarely act in only one place in the body. The same chemistry that helps in one organ can cause an unwanted effect elsewhere. Age, other medicines, kidney and liver function and genetics all change how strongly this happens.
It helps to write down what you noticed, when it started and how it relates to your doses. That short note is far more useful to a pharmacist than trying to remember in the moment.
Never stop a prescribed medicine suddenly without advice. Some can be stopped safely, others need to be reduced gradually or swapped for an alternative.
In the UK you can report a suspected side effect yourself through the Yellow Card scheme. Reports from patients are taken seriously and have led to real changes in how medicines are used.
If something here worries you
This is general information. For advice about your own health or medicines, speak to your GP or pharmacist.
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