Overview

On this page there is information about:

• herbal remedies and products – these contain active ingredients made from plant parts, such as leaves, roots or flowers. Being ‘natural’ does not always mean that they’re safe for you to take.
• dietary supplements – these include probiotics (live microbials) that you find in probiotic yoghurts or as separate capsules, plant materials and extracts, vitamins, and minerals. 

Read the NHS information about vitamins and minerals

Just like conventional (pharmaceutical) medicines, herbal products will have an effect on your body, and might be harmful. Herbal products and nutritional supplements are not tested in the same way as pharmacy and prescription medicines. Usually, they aren’t checked as thoroughly to see how they might cause side effects or interact with your conventional medicines.

There might be interactions between your conventional medicines and herbal products or supplements. They might make your medicines less effective, and so they will not be able to treat your condition properly. They may also increase the risk of you having side effects.

If you want to take supplements for a new symptom, please talk to the healthcare professional who prescribes your medicines. They might be able to make some changes to your prescribed medicines to help ease the symptoms that are bothering you. 

Herbal products and other dietary supplements

This includes non-vitamin and non-mineral supplements, such as:

• plant extracts
• mushrooms
• probiotics
• fish oil products

Most herbal products are not recommended by the NHS and cannot be prescribed. This is because not all herbal or dietary supplements are regulated. These products do not need a licence, and the ones manufactured outside the UK might not be subject to any regulation.

There’s also limited evidence about how effective herbal products and supplements are. Some herbal products are thought to have clinical benefits, but this is not well researched. It’s not possible to predict all the clinical or toxic effects.

There are an increasing number of fake, substandard, unlicensed or contaminated medicines for sale in high street shops. This risk is even higher if you buy medicines online or by mail order.

Herbal products and dietary supplements in elective surgery

There’s limited information available on the safety of taking herbal products and dietary supplements if you are having a surgical procedure or an anaesthetic.

Some problems that herbal products and dietary supplements might cause are:

• blood clotting issues
• effects on how well your wound heals

Herbal products should not be restarted until you have recovered fully from the surgery, and your wounds have healed.  

Pregnancy and breastfeeding

If you’re pregnant, breastfeeding, think you might be pregnant, or are planning to have a baby, we do not recommend taking any herbal products or dietary supplements. This is because there is not enough reliable information available about their safety during pregnancy.

Vitamin and mineral dietary supplements

Vitamins and minerals are essential nutrients that your body requires in small quantities to function correctly and maintain good health.

For most people, a balanced diet provides all the necessary nutrients. However, some people need to take extra supplements so that they get enough.

Taking supplements at daily doses far below the recommended daily allowance (RDA, also known as the reference nutrient intake or RNI) is usually safe. However, adding high-dose supplements when you already have a balanced diet can lead to you having too much, which could lead to side effects.

We do not recommend the routine use of vitamin or mineral supplements, unless you have a diagnosed deficiency, or have been advised to take them by your clinical team.

Common dietary supplements

Antioxidants (such as coenzyme Q10, turmeric/curcumin, wheatgrass, and spirulina)

Many supplements are antioxidants or have antioxidant properties. Antioxidants might help prevent cell damage, but may also stop some conventional medicines (for example, ones taken for cancer) from working as well as they should.

Tea

1 or 2 cups a day of green tea, fruit tea or herbal tea are unlikely to affect your treatment. However, larger quantities might provide a big enough dose of the ingredients to affect your treatment. To avoid this, try to have no more than 2 cups of herbal tea a day.

Probiotics

Probiotics contain live bacteria. If you have a weakened immune system, there’s a small risk that these could cause an infection which your body will not be able to fight as well as usual. Probiotics may also affect the balance of the bacteria in your gut. We recommend that probiotic products are not taken if your immune system is weakened from conditions or treatment.

Supplements with oestrogen-like effects

Some herbal medicines act in a way similar to oestrogen (female sex hormone). Taking them might affect hormone-sensitive conditions, such as some breast, uterine, and ovarian cancers.

There‘s not enough reliable information, so we recommend that people with hormone-sensitive conditions avoid taking supplements that act like oestrogen (have oestrogenic effects). Examples of these include:

• flaxseed
• ginseng
• isoflavones
• liquorice
• milk thistle
• red clover
• soya
• turmeric

Homeopathy

In homeopathy, a substance that in normal doses could cause an undesirable symptom is used in very small amounts to treat that symptom. For example, something that can cause vomiting (being sick) is used in homeopathic doses to prevent or treat nausea and vomiting. In homeopathy, the belief is that the weaker (more diluted) a preparation is, the stronger it is. This is different to conventional medicines, where a bigger dose of a medicine would be expected to have a greater effect.

The strength of products is labelled with a number, followed by an x or c. Products of a strength less than 12c or 24x might interact with conventional medicines and should not be taken.
The dilution numbering system for homeopathic products can be confusing, so if you‘re not sure about a product, do not take it without checking with your clinical team.

There is no legal regulation of homeopathic practitioners in the UK.

Chinese medicines

Traditional Chinese medicine (TCM) is a mixture of herbal medicines and non-medicinal approaches, such as tai chi and acupuncture.        

TCM is known to usually have low-quality studies to support their use, and some have been found to contain undeclared ingredients, such as

• high-risk medicines, like steroids
• toxins, such as arsenic, lead, pesticides and sulphites

For these reasons, we do not recommend the use of TCM.

Choosing herbal medicines or dietary supplements

Herbal medicines carrying a Traditional Herbal Registration (THR) mark will comply with some of the safety and manufacturing standards applied to medicines. Claims made by THR products are based on traditional use and not on evidence of clinical effectiveness.

Herbal medicines carrying a UK Product Licence (PL) number will meet some safety and quality checks.

If you want to take herbal medicines or dietary supplements, we advise you to:

• continue taking your conventional medicines
• avoid use during pregnancy and breastfeeding
• only choose products with a PL number or a THR registration on the label
• only buy products from registered pharmacies, due to the risk of fake medicines
• avoid switching brands or products
• report any suspected side effects using the Yellow Card Scheme[HP4] , either yourself or via a healthcare professional, such as your pharmacist, nurse or doctor

If you suspect a product is a fake, please refer to the MHRA Fake Medicines campaign at www.fakemeds.campaign.gov.uk/ 

Support and more information

The British Dietetic Association have lots of information about supplements,
www.bda.uk.com/resource/supplements.html

NHS information about herbal medicines
www.nhs.uk/tests-and-treatments/herbal-medicines/

NHS information about complementary and alternative medicine
https://www.nhs.uk/tests-and-treatments/complementary-and-alternative-medicine/

Disclaimer

We cannot take any responsibility for decisions you make about taking any herbal, complementary or alternative medicines. If you decide to take any, we would strongly recommend that you speak to your healthcare team to get advice first.