Side Effects: What’s Expected and When to Seek Help
Most medications can cause side effects. In many cases these are mild, temporary, and improve as your body adjusts to treatment. However, some symptoms may indicate that a medicine is not suitable or that further assessment is needed.
This page explains common side effects, how GPs assess their significance, and when you should seek medical advice or urgent help.
These articles are intended as educational sources, not diagnostic nor taking place of a proper medical assessment. If you need help, please book an appointment with one of our GP’s.
Why side effects happen
Medicines work by affecting processes in the body. The same mechanisms that improve symptoms can also cause unwanted effects, particularly when treatment is first started or doses are changed.
Side effects vary between individuals. What one person tolerates well may be problematic for another. This is why follow-up and review are important parts of prescribing.
Common and expected side effects
Many medicines cause mild side effects that are expected and often settle within days or weeks. Examples include:
- nausea or stomach upset
- headache
- dizziness or lightheadedness
- mild drowsiness
- changes in bowel habit
A GP will usually explain what side effects to expect and how long they may last.
Side effects that may need review
Some side effects do not require emergency care but should be discussed with a GP, particularly if they persist or worsen.
These may include:
- ongoing gastrointestinal symptoms
- sleep disturbance or fatigue
- mood changes
- skin reactions that are mild but persistent
- symptoms that interfere with daily activities
In these situations, a medication may need adjusting, changing, or stopping.
When side effects become a safety concern
Certain symptoms suggest a higher risk of harm and need prompt assessment. These may include:
- severe or worsening symptoms
- new neurological symptoms such as confusion or weakness
- unexplained bleeding or bruising
- chest pain or significant breathlessness
A GP can advise whether symptoms are likely to be medication-related and what action to take.
Allergic reactions and severe side effects
True medication allergies are uncommon but can be serious. Symptoms such as swelling of the lips or tongue, difficulty breathing, collapse, or a rapidly spreading rash require urgent medical attention.
If you have previously experienced a drug allergy, this should always be shared with your GP before starting new medication.
What to do if you are worried about side effects
Do not stop prescribed medication abruptly unless advised, as this can sometimes cause harm. If you are concerned about side effects, a GP can help assess:
- whether symptoms are likely medication-related
- whether they are expected or concerning
- whether treatment should continue, change, or stop
Clear advice can help avoid unnecessary worry while keeping you safe.
Side effects in remote GP care
Many side effects can be safely assessed during a remote GP consultation. However, some symptoms require physical examination, observations, or urgent assessment.
If remote assessment is not appropriate, this will be explained and next steps advised.
When to contact a GP
You should consider contacting a GP if:
- you develop new or unexpected symptoms after starting a medication
- side effects are persistent or worsening
- symptoms interfere with daily life
- you are unsure whether it is safe to continue treatment
If symptoms are severe, sudden, or involve breathing difficulty, collapse, or severe swelling, seek urgent or emergency care.
Further Reading and Hub Links
Visit our Medication and Prescribing hub or browse more health topics in the AccessGP Knowledge Base.
If you are worried about side effects or unsure whether a medication is right for you, a GP can help guide you on the safest next step.
Last reviewed by Dr Zamiel Hussain, GMC registered GP
Updated: 8 February 2026