Liquorice extract is used as a sweetener and flavouring agent in some lollies and herbal teas. It is also marketed as a dietary supplement.
- Eating small amounts of liquorice now and again is safe for most people, but it may be harmful if you eat large amounts or if you are taking some medicines.
- Liquorice can interact with some medicines, herbs and dietary supplements.
- Liquorice can cause low blood potassium, abnormal heart rhythms, muscle cramps and weakness, high blood pressure and water retention.
- You are most at risk of side effects from liquorice if you have heart failure or high blood pressure, including high blood pressure during pregnancy. If you have these conditions, you should avoid liquorice.
- If you have been eating a lot of black liquorice or tea with liquorice extract and have heart palpitations, muscle weakness or other health-related problems, stop eating it immediately and seek medical advice.
What is liquorice?
Liquorice extract is derived from the plant Glycyrrhiza glabra. Liquorice extract is used as a sweetener and as a flavouring agent in some lollies and herbal tea and is also marketed as a dietary supplement.
What are the side effects of liquorice?
Liquorice extract, especially when consumed in large quantities, can cause side effects. Glycyrrhizin in liquorice can cause the potassium levels in your body to fall. When that happens, you may experience abnormal heart rhythms, as well as high blood pressure, water retention and swelling (oedema), extreme tiredness and heart failure.
You are most at risk of side effects from liquorice and should avoid it if you have:
- high blood pressure, including high blood pressure during pregnancy
- heart failure.
In general, a maximum of 100 mg/day glycyrrhizin is recommended, which is about 60–70 g of liquorice sweets1.
Liquorice can interact with some medicines, herbs and dietary supplements
Liquorice can interact with some medicines used to treat high blood pressure or heart failure, such as diuretics (also called water pills), digoxin and fludrocortisone. It can also interact with some herbs and dietary supplements. Get advice from your GP or pharmacist if you have questions about possible interactions with a medicine or supplement you're taking.
- Liquorice – all sorts of side effects and interactions Medsafe Prescriber Update, NZ, 2019
- Licorice root National Institutes of Health, US, 2016
- Can eating too much black liquorice be bad for you? NHS, UK, 2018
Angela is a pharmacist in the Quality Use of Medicines Team at Waitematā District Health Board. She has experience in hospital pharmacy in New Zealand and in the UK, and was previously a medical writer for Elsevier in The Netherlands. Angela is interested in promoting the safe use of medicines, particularly high-risk medicines.