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Herbal medicines

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All of Healthily's articles undergo medical safety checks to verify that the information is medically safe. View more details in our safety page, or read our editorial policy.

Herbal remedies are medicines made up of plants, trees or fungi. However, being "natural" doesn't necessarily mean they're safe for you to take.

Herbal remedies, just like pharmaceutical medicines, will have an effect on the body and can potentially be poisonous.

They should therefore be used with the same care and respect as pharmaceutical medicines.

If you're consulting your doctor or pharmacist about health matters, or are about to undergo surgery, always tell them about any herbal medicines you're taking.

If you're taking or plan to take any herbal medicines, be aware of the following:

  • they may cause problems if you are taking other medicines. Mixing could result in reduced or enhanced effects of the medicine(s), including potential side effects
  • you may experience a bad reaction or side effects after taking a herbal remedy
  • as with all medicines, herbal remedies should be kept out of sight and reach of children

Should I avoid herbal medicines?

The safety of many herbal medicines has not been established in certain key groups, including:

  • pregnant women
  • breastfeeding mothers
  • children
  • the elderly

Also, as a rule, anyone with a history of liver or kidney complaints, or any other serious health condition, is advised not to take any herbal medicine without speaking to their doctor first.

If you're buying a herbal remedy...

Look out for a Traditional Herbal Registration (THR) marking on the product packaging – this means the herbal remedy has been assessed against quality standards, and you'll have information about how and when to use it.

THR products do not require the supervision of a medical practitioner.

You can find THR registered products in your local health shop, pharmacy or supermarket (there will be a THR number on the packet).

The claims made for THR products are based on traditional usage and not on evidence of the product's effectiveness. Using them for more serious conditions could put you at risk, especially if you delay seeking advice from a medical practitioner.

Reporting an adverse reaction

In the UK, you can report any side effect or adverse reaction to a herbal medicine using the Yellow Card Scheme.

The Yellow Card Scheme is run by the Medicines & Healthcare products Regulatory Agency (MHRA) – a UK government agency.

The purpose of the Yellow Card Scheme is to act as an early warning system so the MHRA can identify new side effects or risks associated with medicines, including herbal remedies.

You should report adverse reactions or side effects if:

  • you suspect the side effect or adverse reaction was caused by a medicine or herbal remedy you were taking
  • the herbal remedy causes problems severe enough to interfere with everyday activities
  • the side effect occurs when you’re taking more than one medicine or herbal remedy

It's important to include as much detail as possible, particularly any brand name or manufacturer's details relating to the herbal remedy.

Each Yellow Card report helps the MHRA investigate possible safety issues associated with medicines. In the past, these reports have been used to identify interactions between St John's wort and other medicines.

Reports have also highlighted the use of mercury, lead and arsenic in unlicensed Ayurvedic and traditional Chinese medicines. The inclusion of these metals, or salts containing them, poses a serious risk to public health (see box on this page).

Risks of buying herbal remedies online and via mail order

The risks of obtaining fake, substandard, unlicensed or adulterated (contaminated) medicines are increased by buying medicines online or via mail order. Unlicensed herbal medicines manufactured outside the UK may not be subject to regulation.

Drugs and herbal remedies sold online may contain banned ingredients and toxic substances. They may be copies of licensed drugs, but made in unlicensed factories with no quality control.

Some websites may appear to be legitimate but are fronted by bogus doctors or pharmacists.

Herbal slimming products and sexual health products, for example, are best avoided.

Many herbal slimming pills and erectile dysfunction (impotence) remedies have been found to contain dangerous unknown ingredients. Examples include:

  • slimming products containing sibutramine – this drug was withdrawn from the market in January 2010 due to increased risk of heart attack and stroke
  • slimming products containing phenolphthalein – this has previously been used as a laxative, but is no longer authorised for sale in the UK as it may cause cancer
  • sexual health products containing the "Prescription Only Medicines" tadalafil and sildenafil – both of which can cause side effects and should only be used when prescribed by a doctor

If you're to undergo surgery

It's important to tell your doctor if you take any herbal medicines before undergoing surgery.

In some cases, it may be necessary to discontinue the herbal medicine several weeks before surgery. It's thought some could cause complications by interfering with anaesthetics, anticoagulants and other substances used before, during or after procedures.

There are also concerns that some herbal medicines may interfere with blood clotting and blood pressure. For example, garlic, ginseng and ginkgo reportedly interfere with blood clotting mechanisms and may increase the risk of bleeding during surgery.

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Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.