Activated charcoal is used in hospitals as an emergency treatment for certain poisonings and overdoses, where it binds the substance in the stomach before it can be absorbed. It is also sold over the counter as tablets, capsules and powder for wind and bloating, where the evidence is much weaker.
What is Charcoal?
Activated charcoal is not the charcoal used for braais. It is produced by heating a carbon source — wood, coconut shell, peat — and then “activating” it with steam or chemicals at high temperature. This creates an enormous network of tiny pores, giving a single gram a surface area of several hundred square metres.
That surface area is the entire point. Activated charcoal works by adsorption — molecules stick to its surface, rather than being absorbed into it. Substances bound to charcoal in the gut cannot cross into the bloodstream, and pass out in the stool instead.
It is not absorbed by the body at all. It passes straight through, which is why it is well tolerated but also why it can only act on what is still in the digestive tract.
Products vary considerably — tablets, capsules and loose powder, at different strengths, some sold as medicines and some as supplements. Check your own pack.
Two important limitations follow from how it works:
- Timing is everything in poisoning. Charcoal can only bind a substance still in the stomach or upper gut. Given within about an hour of ingestion it can bind a substantial proportion; hours later, it is largely too late.
- It does not bind everything. Alcohol, iron, lithium, strong acids and alkalis, and petroleum products are poorly adsorbed, so charcoal is of little use for those.
What is Charcoal commonly used for?
Its established medical use is in poisoning and overdose, given in hospital or by emergency services. It is a genuinely important treatment — but it is given by trained staff who can judge whether it is appropriate and protect the airway.
Do not give activated charcoal at home to someone who has taken an overdose or swallowed a poison. Call emergency services or a poison centre. Charcoal given to someone drowsy or vomiting can be inhaled into the lungs, causing severe and sometimes fatal pneumonitis. The right action is to get them to medical care with the container or packaging.
Over-the-counter uses, where evidence is considerably weaker:
- Wind, bloating and flatulence — the most common reason people buy it. Evidence is mixed and modest at best.
- Indigestion and general digestive discomfort.
- Diarrhoea, where it is sometimes used, though rehydration is what matters.
- “Detox” and cleansing claims. These are not supported. The body has a liver and kidneys, which perform this function, and charcoal cannot reach substances already absorbed into the bloodstream. Charcoal in food and drink products is decorative rather than functional.
- Teeth whitening, in charcoal toothpastes and powders. Dentists generally advise against these — charcoal is abrasive and can wear enamel, which does not grow back, and worn enamel exposes the yellower dentine underneath, making teeth look darker over time.
- Wound dressings, where charcoal-impregnated dressings genuinely help absorb odour from malodorous wounds.
How Charcoal fits into this medicine category
| Group | Examples | Role |
|---|---|---|
| Adsorbents | Activated charcoal, kaolin (Pectrolyte) | Bind substances in the gut |
| Antiflatulents | Simeticone | Break up gas bubbles |
| Antacids | Calcium/magnesium salts | Neutralise stomach acid |
| Acid reducers | Omeprazole, cimetidine | Reduce acid production |
| Antispasmodics | Hyoscine | Relieve gut cramping |
| Oral rehydration | ORS sachets | Replace fluid and salts in diarrhoea |
If bloating and wind are the problem, simeticone or dietary changes are usually more effective. See the general medicines hub and the HP553 guide.
What to check before using Charcoal
Separate it from all other medicines by at least two hours. This is the most important practical point. Charcoal does not distinguish between a poison and your prescription — it binds medicines just as effectively, and can substantially reduce or abolish their effect.
This matters especially for:
- The contraceptive pill. Reduced absorption could mean reduced protection.
- Thyroid medicine, epilepsy medicines, heart medicines and antibiotics, where a missed effective dose has consequences.
- Any medicine you rely on daily.
Drink plenty of water with it, as it can cause constipation.
Speak to a pharmacist or doctor first if you:
- Take any regular medicine.
- Have a bowel obstruction, reduced gut motility, or are severely constipated — charcoal can worsen these.
- Have had recent bowel surgery.
- Have persistent digestive symptoms that have not been assessed.
- Are pregnant or breastfeeding.
- Are giving it to a child.
- Have swallowing difficulties, or are drowsy for any reason.
Do not use it to treat a suspected poisoning at home. Call emergency services or a poison centre.
Possible cautions and when to ask a pharmacist or doctor
Activated charcoal is generally well tolerated. Expected effects include black stools — harmless, but worth knowing so it is not mistaken for the black tarry stools of gastrointestinal bleeding — and constipation, plus black staining of the mouth and teeth.
Seek medical attention if you develop:
- Constipation that does not resolve, or abdominal pain with a swollen abdomen.
- Vomiting after taking it, particularly if drowsy — there is a risk of inhaling it.
- Coughing, wheezing or breathlessness after taking it — possible aspiration into the lungs, which needs urgent assessment.
- Black stools when you have not taken charcoal, which may indicate bleeding.
See a doctor rather than self-treating if you have:
- Persistent bloating or a change in bowel habit, particularly over 45.
- Unintended weight loss.
- Blood in the stool.
- Severe or worsening abdominal pain.
- Symptoms lasting more than two weeks.
In a suspected poisoning or overdose, contact emergency services or a poison centre immediately, and take the container or packaging. This applies even if the person seems entirely well — several serious poisonings, paracetamol among them, produce no early symptoms while causing significant harm.
Related medicine guides
Frequently asked questions
What are charcoal tablets used for? They are sold over the counter for wind, bloating and indigestion, where evidence is modest. Activated charcoal’s established use is in hospital treatment of certain poisonings.
What is charcoal powder used for? The same purposes, and in hospital settings for poisoning. It is also used in charcoal-impregnated wound dressings to absorb odour.
Does activated charcoal detox the body? No. It cannot reach substances already absorbed into the blood, and the liver and kidneys perform this function. Charcoal in food and drinks is decorative.
Can I use it for an overdose at home? No. Call emergency services or a poison centre. Charcoal given to someone drowsy or vomiting can be inhaled and cause serious lung damage.
Does it affect my other medicines? Yes — significantly. It binds medicines as readily as toxins. Separate it from all other medicines by at least two hours, including the contraceptive pill.
Is charcoal toothpaste good for whitening? Dentists generally advise against it. Charcoal is abrasive and can wear enamel, which does not regrow, ultimately making teeth look darker.
Why are my stools black? Activated charcoal turns stools black, which is harmless. Black tarry stools when you have not taken it can indicate bleeding and need medical attention.
Is it the same as braai charcoal? No. Activated charcoal is specially processed to create an enormous porous surface area. Never eat barbecue charcoal.