Medicine Overdose Symptoms

A medicine overdose happens when someone takes more than the recommended or prescribed amount of a medicine, or when enough of a medicine builds up in the body to cause harmful effects. An overdose can be accidental or intentional, and the symptoms can range from mild to life-threatening.

If you think you or someone else may have taken too much medicine, get medical advice immediately rather than waiting for symptoms to appear. Some medicines can cause serious poisoning before obvious symptoms develop. In South Africa, the Poisons Information Helpline is available 24 hours a day on 0861 555 777. For a medical emergency, call 112 from a cellphone or 10177 for an ambulance.

Loss of consciousness, difficulty breathing, seizures, severe confusion, collapse or rapidly worsening symptoms require emergency medical attention.

For more information about high-risk reactions, see the guide to serious medication side effects.

How medicine overdose symptoms can be linked to medicines or supplements

Medicine overdose symptoms vary considerably depending on the product involved, the amount taken, the person’s age and health, and whether other medicines, supplements, alcohol or substances were also taken.

Possible symptoms can include:

• nausea or vomiting
• stomach pain or diarrhoea
• unusual sleepiness or difficulty staying awake
• dizziness or poor coordination
• confusion or unusual behaviour
• agitation, restlessness or tremors
• blurred vision
• sweating or unusually hot, dry skin
• a very fast or very slow heartbeat
• difficulty breathing or unusually slow breathing
• weakness or fainting
• seizures
• loss of consciousness

These symptoms are not specific to overdose. Many can also occur with illness, ordinary medication side effects or other medical conditions. What makes an overdose particularly important is the possibility that too much medicine has been taken, even if the person currently feels well.

An overdose does not always cause immediate symptoms

Do not assume that everything is fine because there are no symptoms yet. The effects of poisoning can sometimes take hours or even days to become apparent.

Paracetamol is an important example. Taking too much can cause severe liver injury, yet some people initially have few or no symptoms. When symptoms do occur, they may include nausea, vomiting, abdominal pain, confusion or jaundice, and serious effects can be delayed.

This is one reason a suspected overdose should be assessed according to what was taken and how much may have been taken, rather than according to symptoms alone.

How accidental medicine overdoses can happen

Taking too much medicine is not always deliberate. Accidental overdose may occur when someone:

• accidentally takes a dose twice
• misunderstands the dosing instructions
• takes several products containing the same active ingredient
• uses a prescription medicine differently from the prescribed instructions
• gives a child an incorrect amount
• accidentally takes somebody else’s medicine
• combines medicines or supplements in a way that increases toxicity
• continues taking a medicine that is accumulating in the body because it is not being cleared normally

Cold, flu and pain products deserve particular attention because different brands may contain the same active ingredient. For example, paracetamol can appear in both stand-alone pain medicines and combination products, making accidental duplication possible.

Medicines and product categories that may be associated with this symptom

Almost any medicine can cause harmful effects if enough is taken, but the pattern of symptoms depends strongly on the medicine involved.

Pain and fever medicines

Pain medicines include several different drug groups, and overdose symptoms are not the same for all of them.

Too much paracetamol can cause serious liver damage, sometimes before obvious symptoms appear. Other pain medicines may cause stomach, kidney, nervous-system or breathing problems depending on the active ingredient and amount involved.

Opioid pain medicines and sedating medicines

Medicines that suppress the central nervous system may cause marked drowsiness, slowed breathing, poor responsiveness or unconsciousness when taken in excessive amounts. Breathing problems or an inability to wake the person are medical emergencies.

Antidepressants and other mental-health medicines

An overdose involving certain psychiatric medicines may cause drowsiness, agitation, confusion, abnormal heart activity, tremors or seizures. The exact risks differ considerably between medicines, so professional advice should be based on the specific product involved.

Cold, flu, allergy and combination medicines

Combination products can contain several active ingredients. Depending on the ingredients, excessive amounts may cause drowsiness, agitation, changes in heart rate, confusion, nausea or other toxic effects.

Always give the healthcare professional or poison-information specialist the exact product name and active ingredientsif you can find them.

Diabetes medicines

Too much of some glucose-lowering medicines can cause dangerously low blood sugar. Possible warning signs include sweating, shaking, confusion, abnormal behaviour, severe weakness, seizures or loss of consciousness.

Heart and blood-pressure medicines

Some cardiovascular medicines can affect blood pressure and heart rate when taken in excessive amounts. Symptoms may include dizziness, weakness, fainting, unusual tiredness or a heartbeat that is much slower or faster than expected.

Supplements and herbal products

“Natural” does not mean risk-free. Vitamins, minerals, herbal preparations and other supplements can also cause poisoning when excessive quantities are taken, and they may interact with medicines.

When seeking help, mention all products involved, including prescription medicines, pharmacy medicines, vitamins, minerals, herbal products and supplements. MedlinePlus specifically advises that healthcare professionals be told about medicines, vitamins and supplements because interactions and excessive exposure can contribute to harmful effects.

Red flags: when this symptom may need urgent medical attention

A suspected overdose should be discussed with a poison-information service or healthcare professional promptly, even if no symptoms are present.

Call emergency services immediately if the person:

• is unconscious or cannot be woken
• has stopped breathing or is struggling severely to breathe
• has a seizure
• collapses or faints repeatedly
• develops severe confusion or becomes extremely difficult to manage
• has blue or grey lips or other signs of inadequate breathing
• develops severe chest pain
• deteriorates rapidly

Emergency poisoning guidance recommends immediate assessment because symptoms can be delayed and some overdoses can become life-threatening.

In South Africa, call 112 from a cellphone or 10177 for an ambulance in an emergency. The Poisons Information Helpline on 0861 555 777 provides 24-hour poisoning advice to the public and healthcare professionals.

You can also read more about when to see a doctor for medication side effects.

Children, older adults and vulnerable people

Seek professional advice promptly if a suspected overdose involves a child, an older adult, a pregnant person, someone with kidney or liver disease, or someone taking several medicines.

If the overdose was deliberate, or there are concerns about self-harm or suicidal thoughts, treat the situation as an emergency. Do not leave the person alone while emergency help is being arranged.

What to track before speaking to a doctor or pharmacist

Information about the medicine can help healthcare professionals assess the risk more accurately.

If possible, have the following information ready:

• the exact medicine or product name
• the active ingredient and strength shown on the packaging
• approximately how much may have been taken
• the usual prescribed or recommended dose
• the approximate time the medicine was taken
• whether more than one medicine or supplement was involved
• any alcohol or other substances that may also have been used
• the person’s age and approximate weight, especially for a child
• current symptoms and when they began
• relevant medical conditions
• other medicines and supplements normally being used

Keep the medicine packaging, blister packs, bottles or patient-information leaflet available. Poisoning guidance recommends identifying the substance and taking its packaging with the patient where possible.

Do not delay an emergency call because some of this information is unavailable. Give the healthcare professional whatever information you have.

What not to do without medical advice

When a medicine overdose is suspected, avoid trying to treat the situation yourself.

Do not deliberately make the person vomit. Vomiting can create additional risks, including choking. Poisoning guidance from the NHS and MedlinePlus advises against inducing vomiting unless specifically directed by a healthcare professional or poison-information specialist.

Do not:

• give food, drinks, milk or home remedies unless instructed to do so
• give another medicine in an attempt to “counteract” the overdose
• guess whether the next scheduled prescription dose should be changed
• wait for severe symptoms before asking for advice
• assume a supplement or herbal product cannot cause poisoning
• rely only on internet information to decide that an overdose is safe

If there is uncertainty about future doses of a regular prescription medicine, ask the poison-information specialist, doctor or pharmacist what to do rather than changing the treatment plan yourself.

Related side-effect guides and reporting options in South Africa

After the immediate overdose risk has been medically assessed, it may be useful to understand whether symptoms could represent a medicine reaction, interaction or another safety problem.

The side effect symptoms A–Z can help you explore other symptom-led medicine safety information.

If a suspected adverse reaction or medicine-safety problem needs to be reported, South Africa’s health-products regulator, SAHPRA, accepts adverse-event reports from members of the public and healthcare professionals. SAHPRA provides an electronic reporting route as well as an adverse drug reaction reporting form.

See the guide on how to report side effects in South Africa for the local reporting process.

Reporting a suspected adverse reaction is not a replacement for emergency treatment. Deal with an overdose or serious symptoms first.

Frequently asked questions about medicine overdose symptoms

Is an overdose a common side effect?

No. A side effect can occur when a medicine is taken at the recommended dose. An overdose refers to taking more than the recommended amount, or otherwise having enough of the medicine in the body to cause harmful effects.

How long can medicine overdose symptoms last?

There is no single timeframe. Symptoms and recovery depend on the medicine, amount taken, timing, individual health factors and treatment received. Some effects appear quickly, while others may be delayed for hours or days.

Should I stop my regular medicine after accidentally taking too much?

Do not guess about future doses of a prescription medicine. Contact the Poisons Information Helpline, your doctor or a pharmacist and give them the exact medicine, strength, amount and timing. They can advise you about the next dose based on the specific medicine and circumstances.

When should I seek help?

Seek advice immediately whenever a potentially harmful amount of medicine may have been taken, even if the person currently feels well. Call emergency services for severe breathing problems, seizures, unconsciousness, collapse or other rapidly worsening symptoms.

South African emergency contacts: Poisons Information Helpline 0861 555 777 (24 hours); emergency from a cellphone 112; ambulance 10177.

This information is for general education and does not diagnose or treat a medicine overdose. If you think you or someone else may have taken too much medicine, contact a poison-information service, doctor, pharmacist or emergency service promptly. Do not delay urgent medical care while trying to identify symptoms online.