Dosage
Dosage for senna tablets and syrup you buy (self treatment)
The usual dose of senna tablets and liquid for constipation is:
- adults and children aged 12 years and over – 1 or 2 tablets (7.5mg or 15mg) at bedtime (or 1 tablet of Senokot Max Strength)
- adults and children aged 12 years and over – one or two 5ml spoonfuls (7.5mg or 15mg) of syrup at bedtime
If you have not taken senna before, start with one 7.5mg tablet or one 5ml spoonful of syrup. If that does not work you can increase the dose to a maximum of 2 tablets or two 5ml spoonfuls at bedtime.
Important: Information for ages 12 to 17
Only give senna that you buy to a young person aged 12 to 17 years if a doctor or pharmacist recommends it.
Dosage for senna tablets prescribed by a doctor
The usual starting dose is:
- adults aged 18 years and over – two 7.5mg tablets, taken once a day at bedtime
- children aged 6 to 17 years – one 7.5mg tablet, taken once a day at bedtime
A doctor may prescribe higher doses for adults and children up to a maximum of 4 tablets (30mg) taken once a day if necessary.
Dosage for senna syrup prescribed by a doctor
The usual dose is:
- adults aged 18 years and over – one or two 5ml spoonfuls (7.5mg or 15mg) at bedtime
- children aged 4 to 17 years – 2.5ml (half a 5ml spoonful) to two 5ml spoonfuls at bedtime
- children aged 1 month to 3 years – 2.5ml (half a 5ml spoonful)
Sometimes, adults and children may need higher doses.
The maximum dose is:
- adults aged 18 years and over – up to four, 5ml spoonfuls
- children aged 4 years to 17 years old – four, 5ml spoonfuls
- children aged 1 month to 3 years old – two, 5ml spoonfuls given once a day at bedtime
Senna syrup comes with a plastic cup or spoon to measure the dose. Do not use a kitchen spoon as it will not measure the right amount.
How to take it
Take senna once a day at bedtime. You can take it with or without food.
Senna takes about 8 hours to work. It's usual to take it at bedtime so it works overnight.
Drink plenty of fluids (6 to 8 glasses a day) while you're taking senna or your constipation may get worse.
How long to take it for
Take senna for a few days only and no longer than a week. If you take it for longer, your body can start to rely on it, rather than your bowels doing the work on their own.
If you are still constipated after taking senna for 3 days, talk to your doctor.
If you forget to take it
If you forget a dose of senna, just skip the missed dose and take the next dose the following evening.
Never take 2 doses at the same time. Never take an extra dose to make up for a forgotten one.
If you often forget doses, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.
If you take too much
Taking an extra dose of senna is unlikely to harm you.
You may get stomach pain and diarrhoea but this should ease off within 1 or 2 days.
If you're worried, talk to your doctor or a pharmacist.