Infections
Medicines for Giardiasis
A gut infection caused by a parasite, often picked up from contaminated water or food while travelling, causing prolonged diarrhoea and bloating — treated with specific medicines.
Education and reference only. This explains which medicines are used and why, in plain language — it deliberately contains no doses and is not a substitute for advice from your doctor or pharmacist. Always discuss your own treatment with a qualified clinician, and check the BNF and the product labelling for prescribing detail.
Quick answer
What is Giardiasis?
Giardiasis is an infection of the gut caused by a microscopic parasite (Giardia), spread through swallowing water or food contaminated with it, or through close contact with an infected person. It is a common cause of persistent travellers' diarrhoea, and can also be caught from untreated water (such as streams or lakes) and in places with poorer sanitation.
- How it is treated: Giardiasis is treated with a course of specific anti-parasitic medicine, which clears the infection in most people, alongside staying hydrated and eating as able.
- Self-care: Drinking safe or treated water (avoiding untreated streams and lakes), good hand hygiene, and careful food practices when travelling all prevent giardiasis.
- When to seek help: See a GP for diarrhoea, bloating and cramps lasting more than a few days, especially after travel or contact with untreated water, so a stool test can be done.
What it is
Giardiasis is an infection of the gut caused by a microscopic parasite (Giardia), spread through swallowing water or food contaminated with it, or through close contact with an infected person. It is a common cause of persistent travellers' diarrhoea, and can also be caught from untreated water (such as streams or lakes) and in places with poorer sanitation. Symptoms usually appear a week or two after infection and can include diarrhoea (often foul-smelling and greasy), bloating, excess wind, tummy cramps, nausea and tiredness; some people lose weight if it persists. Symptoms can come and go over weeks. Many infections are mild or symptomless. It is diagnosed by testing stool samples for the parasite.
How it is treated
Giardiasis is treated with a course of specific anti-parasitic medicine, which clears the infection in most people, alongside staying hydrated and eating as able. Because it can spread easily, good hand and food hygiene helps prevent passing it on, and household members with symptoms may also need testing and treatment. Occasionally symptoms persist and a repeat or alternative course is needed, and some people have temporary lactose intolerance afterwards while the gut recovers. Prevention is important for travellers: drinking safe water, avoiding untreated water (including when swimming or camping), and good hand hygiene, especially before eating and after using the toilet.
For this condition, these medicines
Medicine classes used for Giardiasis
Each links to a full, dose-free guide — what it is, how it works, who can and cannot use it, side effects, interactions and FAQs.
Beyond medication
Lifestyle and self-care
Drinking safe or treated water (avoiding untreated streams and lakes), good hand hygiene, and careful food practices when travelling all prevent giardiasis. During recovery, staying hydrated and temporarily avoiding dairy if it worsens symptoms can help.
When to get help
When to see a doctor
See a GP for diarrhoea, bloating and cramps lasting more than a few days, especially after travel or contact with untreated water, so a stool test can be done. Seek care for signs of dehydration or persistent weight loss.
Not sure how urgent it is? It is always OK to call NHS 111 for advice, day or night.
Answers
Giardiasis: frequently asked questions
How do you catch giardiasis?
By swallowing water or food contaminated with the Giardia parasite — for example untreated water while travelling, camping or swimming — or through close contact with an infected person.
How is giardiasis treated?
With a course of specific anti-parasitic medicine, which clears it in most people, along with staying hydrated. Good hygiene prevents spreading it to others.
Sources
Where this is drawn from
- NHS — Giardiasis
- TravelHealthPro — Giardiasis
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