Giardiasis can usually be successfully treated using a medicine called metronidazole, which works by killing the parasites that cause the infection.
It is usually taken in tablet form (orally). The recommended course of treatment will depend on factors such as your age and body weight, but it can range from a three to 10-day course.
Your GP or pharmacist will be able to give more detailed instructions for your individual circumstances.
Metronidazole is well tolerated in adults and children. Serious side effects are rare (occurring in less than 1 in a 1,000 people).
The most commonly reported side effects are usually mild ones affecting the digestive system, such as:
- nausea
- vomiting
- diarrhoea
- stomach pain
Tinidazole
If you're unable to take metronidazole, for example, you've previously had an allergic reaction to it, an alternative medication called tinidazole may be recommended.
Most people only need a one to three-day course of tinidazole. The risk of side effects is slightly higher, although these tend to be mild and improve as your body gets used to the medication. Side effects include:
- nausea
- vomiting
- loss of appetite
- diarrhoea
- stomach pain or cramps
- headache
- tiredness
- unpleasant metallic taste in your mouth
- darkening of your urine
See Giardiasis - medicines information for more information about metronidazole and tinidazole.
Cautions
On rare occasions, some people feel dizzy or sleepy while they're taking metronidazole. If this happens to you, avoid driving or using power tools or machinery.
Don't drink alcohol while taking metronidazole or tinidazole, or for 48 hours after finishing your dose. Mixing alcohol with these types of medication can make the side effects worse.
As a precaution, using metronidazole or tinidazole is not recommended during the first three months of pregnancy or if you're breastfeeding.
If you're diagnosed with giardiasis, other members of your household may be advised to have treatment. This may be recommended as a precautionary measure just in case they've also been infected. Your GP will be able to tell you if treatment is necessary.
