Senna stimulates the muscle contractions that move stool along the bowel. It works overnight, which makes it convenient — and it is the laxative people are most likely to end up relying on, which is exactly what it is not designed for.
Short-term relief of constipation, usually where stool is already soft enough but is not moving. It is also used to clear the bowel before certain procedures, under instruction.
If stools are hard and dry, a softening laxative such as macrogol is usually the better starting point — stimulating a bowel full of hard stool tends to cause cramping without much result.
The usual adult dose is taken at bedtime, and it works in around eight to twelve hours — so you go in the morning.
It is intended for short-term use, generally no more than a week without advice. If you need a laxative most weeks, that is worth a conversation about why, rather than a bigger box of senna.
Not for children under 12 without medical advice.
Stomach cramps and colicky pain are the most common effects. Urine may harmlessly change colour.
Do not take senna if you have:
Long-term daily use of stimulant laxatives is best avoided. It is also worth knowing that senna appears in a number of “detox” and slimming teas, which is where some people end up taking it daily without realising what it is.
Senna can be used in pregnancy where a bulk-forming or osmotic laxative has not worked — but check with us or your midwife first, and it is generally avoided in the third trimester.
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