Managing complementary products and conventional medicines

Self-medicating

Some people self-medicate with complementary products due to cultural traditions, spiritual beliefs, or advice from family, friends, or community members. If this is the case, explore further in a non-judgemental and open discussion and offer evidence-based advice.

There may be some misconceptions about either the safety of the complementary product or worries about conventional medicines.

Pregnancy

Herbal products should be avoided unless the benefits outweigh risks. Data relating to the safety of complementary products in pregnancy is limited. 

There are few complementary products that can be taken safely in pregnancy. You can find more information at Best Use of Medicines in Pregnancy (BUMPs) and NHS Vitamins, Supplements and Nutrition in Pregnancy.

Breastfeeding

Herbal products should be avoided as advised by the NHS due to insufficient information on their transfer into breast milk. The risk of side effects in breastfed infants is considered higher for premature or very young babies, and for those with concurrent illnesses. 

Children

Many complementary products are not tested or formulated specifically for children. Adult doses may be inappropriate, and safe children’s dosing is often unknown or not clearly labelled.

Always refer to evidence-based children’s doses.

High risk conditions

Complementary products should not replace conventional medicines which could result in life threatening situations due to loss of control or toxicity. There is no evidence to suggest they can cure high risk conditions such as cancers, cardiovascular disease, diabetes, epilepsy, and HIV.

Using complementary products alongside conventional medicines to control high risk conditions could also result in undocumented interactions, side effects or worsening of the condition.

Hospitalised people

Consult your local Trust Medicines Policy or ICB guidance regarding the use of herbal medicines by in-patients.

Hospitalised people should not take herbal medicines until they have fully recovered as advised by UK Clinical Pharmacy Association.

Perioperative period

People should discontinue complementary products at least 2 weeks before planned surgery.

Some complementary products can cause cardiovascular instability, electrolyte disturbances, coagulation disorders, endocrine effects, liver toxicity, and kidney function complications during surgery.

For example, garlic, ginger and gingko biloba can increase the risk of bleeding during surgery while kava and valerian can impact anaesthesia doses.

Kidney disease

People with kidney disease taking complementary products may be at increased risk of worsening kidney disease. Some products can worsen kidney disease, such as creatine, liquorice root and cat’s claw.

Others may contain potassium or phosphorus which may be restricted in the diet of people with kidney disease.

Liver disease

People with liver disease should be cautious when taking herbal products as advised by the British Liver Trust

Conventional medicines are dose adjusted to account for reduced liver function and other complications. Complementary products may not be and could accumulate to toxic levels.

Some herbal products have been associated with Drug Induced Liver Disease up to 3 to 6 months after stopping. For example black cohosh, kava, and mistletoe.

Failed therapy

People may take complementary products because they feel their current treatment is not fully addressing their symptoms or concerns. If this is the case, review and optimise their current conventional treatments.

You may need to explore other evidence-based options.

Narrow therapeutic index

People who take medicines with a Narrow Therapeutic Index (NTI) such as digoxin, ciclosporin, warfarin and lithium, should avoid taking complementary products. The slightest change in plasma level of an NTI medicine can lead to side effects and toxicity or loss of therapeutic effect.

Other medicines

Other conventional medicines may interact with complementary products to result in loss of effect or increase in side effects and toxicity from the product. Refer to our article on Understanding drug interactions and the BNF tables that list medicines commonly associated with a pharmacodynamic effect.

Product details

Find out the name of the complementary product, the formulation and strength, and all the ingredients. Products with the same name may differ in ingredients.

We may not be able to give safety advice if someone takes several complementary products or complementary ingredients with their usual medicine.

Most published evidence relates to interactions between one complementary product ingredient and one conventional medicine. Anything more than this is likely to require your clinical judgement.

UK banned or not NHS prescribable

Check if the product contains herbal ingredients that are banned or have restricted use in the UK by the MHRA due to concerns about safety.

Homeopathy and herbal ingredients should not be routinely prescribed by the NHS in primary care.

Amount of ingredient

Some complementary products may contain combinations of herbal ingredients, homeopathic dilutions and dietary supplements.

You should review the total daily dose for each ingredient. People taking more than one complementary product may expose themselves to higher than recommended daily doses (RDD).

Dietary supplements will have the RDD listed on the product label or package insert. See the SPS article Understanding food supplements for further information.

The RDD for herbal products can be found in the freely accessible monographs listed in the SPS article Complementary products: resources to support answering questions.

Advise people not to take multiple complementary products to reduce the risk of dosing above the safe amount.

Homeopathic products

The NHS advises there is no good quality evidence to suggest homeopathy is effective as a treatment for any health condition.

There is no evidence of interactions between highly diluted homeopathic products and conventional medicines. The starting material is so diluted that little or no molecules are in the final product.

The MHRA advises homeopathy products may still cause side effects in some people.

Homeopathic products are labelled with ‘homeopathic medicinal product’ to identify them from herbal products containing the same ingredient.

Product quality 

Find out if the product is regulated. More information can be found on our article Explaining the licensed status of medicines.

Traditional Herbal Register (THR)

Complementary products with a Traditional Herbal Registration (THR) are regulated by the MHRA and will comply with the manufacturing standards applied to conventional medicines.

Claims made by THR products are based on traditional use and not on evidence of clinical effectiveness.

Homeopathic regulatory scheme

Homeopathic products must be registered with one of the 2 UK regulatory schemes. Products with homeopathic registrations or authorisations granted by the MHRA are listed in the schemes.

Food supplements

Food supplements are not medicines. They are regulated as foods, not as medicines, but must still meet their description and be safe. See our article Understanding food supplements for further information.

Source of product

If the complementary product has been purchased, find out who the supplier is.

The MHRA highlights risks of buying a fake or adulterated complementary product is increased when bought from non-reputable sources.

Online sources should be registered pharmacies or reputable retailers.

Advise people to follow the Government’s Know what you’re buying tips.

Product cost

Some complementary products are expensive and are not backed up by evidence or require long term use to meet any therapeutic claims.

The NHS does not routinely fund complementary products due to the lack of proven effectiveness.

Some complementary products can affect the absorption, distribution, metabolism and elimination and pharmacodynamics of conventional medicines.

Refer to our article Complementary products: resources to support answering questions to get information on the pharmacokinetics and pharmacodynamics of ingredients in the complementary product.

Use the Summary of Product Characteristics (SmPC) to get information on the pharmacokinetics and pharmacodynamics of conventional medicines.

Use both these pieces of information to decide if the complementary product could affect the pharmacokinetics or pharmacodynamics of the conventional medicine and vice versa.

Involve the person in the decision-making on whether the complementary product should be taken or not.

You may find the common scenarios in our article Advising on complementary products and conventional medicines a useful aid.

Advise the person what they should monitor if they decide to start or continue taking a complementary product with their conventional medicines.

You may find the counselling points on our article Advising on complementary products and conventional medicines useful.