Liver injury from painkillers and herbal products

After absorption from the gut, most medicines pass through the liver, which converts them into forms that can be cleared. Sometimes a by-product of that conversion is itself harmful, or the liver is overwhelmed by too much of a substance. Injury can then follow in one of two broad ways: predictably, when the amount taken is too high, or unpredictably in a small number of susceptible people even at ordinary amounts.

Paracetamol is the standard example of the first, and some herbal products and supplements illustrate the second. Doctors describe both as drug-induced or herbal-induced liver injury. A separate guide on this site covers severe drug reactions affecting the liver.

The NHS describes paracetamol as safe for most people when taken as directed, noting that excessive amounts can sometimes damage the liver. It recommends avoiding paracetamol if you have existing liver conditions or are dependent on alcohol or binge drink, and advises against taking it at the same time as other medicines that contain paracetamol, such as many cold and flu remedies.

The usual route to harm is accidental. A person with a headache, a cold and a sore back takes a combination remedy, a prescription co-codamol-type product and plain tablets in the same day, without realising that all three contain paracetamol. Another route is repeating doses closer together than the leaflet allows during a bad pain flare.

The harm is not always felt early. A person who has taken too much can feel quite well for a day before liver damage declares itself, which is why the advice is to seek help at once rather than wait for symptoms. The NHS tells people to contact 111 if they have taken more paracetamol than the packet or leaflet says.

Anti-inflammatory painkillers such as ibuprofen are better known for stomach and kidney effects than for the liver, though liver problems are possible and the NHS lists liver conditions among reasons ibuprofen may be unsuitable. Its safety advice is to take the smallest amount needed for the shortest time. Combination painkillers that pair paracetamol with an opioid add a further risk because the opioid effect can encourage repeated dosing.

If you have long-term liver disease, are older, drink heavily or take several medicines, ask a pharmacist which painkiller is most suitable for you rather than trying whatever is in the cupboard.

"Natural" does not mean harmless to the liver. The US National Center for Complementary and Integrative Health states that various kava products have been linked to rare cases of liver injury, some serious or even fatal, and lists factors that may contribute, including alcohol- or acetone-based extraction, the plant parts used, concurrent alcohol, contamination or adulteration and genetic susceptibility. It also advises that kava should not be combined with sedatives, benzodiazepines or alcohol.

For green tea, NCCIH notes that liver injury has been documented in some users of green tea products, particularly tablets and capsules, though uncommon, and that drinking tea as a beverage has shown no documented safety concerns for adults. It advises discussing supplements with your healthcare provider, especially if you take other medicines.

In the UK, many herbal products are sold as food supplements rather than licensed medicines, and quality control, strength and labelling can vary between brands. Use reputable sources, avoid products making dramatic claims and report suspected reactions through the Yellow Card scheme.

• Concentrated extracts in capsule or tablet form carry more risk than the food or tea.

• Products combining many ingredients make the culprit harder to identify.

• Imported products bought online may not follow UK quality standards.

• Always tell clinicians about supplements, particularly before surgery or when liver tests are abnormal.

Early symptoms are vague: tiredness, loss of appetite, nausea, abdominal discomfort. More specific signs include yellowing of the skin and whites of the eyes, itching, dark urine and pale stools. The NHS says jaundice can be a sign of something serious such as liver disease and that yellow skin or eyes need urgent medical attention, via 111 or an emergency GP appointment.

Blood tests, called liver function tests, show liver enzymes and bilirubin, and other tests exclude viral hepatitis, alcohol-related disease, gallstones and autoimmune causes. In drug-related injury, the pattern and timing relative to the medicine are key. Recovery usually follows once the cause is stopped, which is why identifying it matters, though severe injury can require hospital care.

A handful of habits prevent most avoidable harm.

• Read the active ingredient on every product and add up paracetamol across all of them.

• Never exceed the amount on the packet and keep to the gaps between doses.

• Keep an up-to-date list of every medicine and supplement for appointments.

• Take extra care with alcohol, existing liver disease and low body weight, and ask a pharmacist.

• Stop a new supplement and seek advice if you develop jaundice, dark urine or severe itching.