Constipation in older adults: common causes, what helps first and when a laxative or a GP is the next step

Why constipation in elderly people is so common

The NHS lists being over 65 as one of the situations when constipation is more likely. According to the NIA, about one in three older adults has symptoms now and then. Most of the time it’s uncomfortable rather than dangerous, and it responds to simple changes.

It’s likely to be constipation if:

• you haven’t had a poo at least 3 times in the last week, or you’re going less often than usual;
• the poo is dry, hard or lumpy, or unusually large or small;
• you strain or it hurts;
• you feel you haven’t fully emptied your bowels.

There’s no “right” number. For some people twice a day is normal, for others three times a week. What matters is a change from your own usual pattern.

If you look after a parent, watch for changes in behaviour. The NHS notes that in older people, and especially in someone with dementia, constipation is easy to miss. New confusion can be a sign of pain or discomfort.

Common causes: medicines, fluids, fibre and moving less

Often several small things add up. A person drinks less to avoid getting up at night, eats softer food, walks less after a fall, and has just started calcium tablets.

Don’t stop a prescribed medicine on your own, even if you suspect it. The NHS says to speak to your GP first. If iron is the problem, our guide to iron tablets covers gentler forms; for calcium, see calcium and vitamin K2.

If a medicine is the cause

Painkillers containing codeine or morphine are the classic example. The NHS says to see a GP if you’re taking a medicine that’s causing constipation. Your GP may change the dose or prescribe a laxative to take alongside it. If you take opioids, check with a pharmacist before choosing a laxative yourself.

Iron and calcium are easier to adjust. Your GP may suggest a different form or a lower dose. NIH ODS says spreading calcium through the day and taking it with meals can ease gas, bloating and constipation. Chewable tablets and calcium antacids count too, so add up all your calcium for the day.

What helps first: fluids, fibre and a daily walk

These are the NHS’s first steps, and they’re safe for almost everyone. You may notice a difference within a few days, although sometimes it takes a few weeks.

Fluids. The NHS Eatwell Guide suggests 6–8 cups or glasses of fluid a day. Water, lower-fat milk and lower-sugar drinks, including tea and coffee, all count. If night-time trips to the toilet worry you, drink more in the morning and early afternoon rather than less overall. If your doctor has told you to limit fluids, for example because of heart failure or kidney disease, keep to that limit.

Fibre. Add it gradually, or wind and bloating get worse. Good choices:

• porridge oats, wholemeal bread, bran or linseed sprinkled on cereal;
• beans, lentils and vegetables with main meals;
• fruits that contain sorbitol, such as apples, apricots, grapes, raisins, raspberries and strawberries.

Adults should aim for 30 g of fibre a day, says the NHS; our psyllium and fibre guide shows how close most people get.

Moving. A daily walk helps the bowels work more regularly. If walking is hard, any extra movement through the day counts.

Toilet routine. Go when you feel the urge, at a regular time, and give yourself plenty of time. Rest your feet on a low stool so your knees sit higher than your hips.

Tick off what you already do:

Fibre for constipation: where psyllium fits

If diet changes aren’t enough and you’re buying a laxative without a prescription, the NHS says a bulk-forming one is usually best to try first. In UK pharmacies that’s ispaghula husk; on iHerb it’s sold as psyllium husk. It makes stools bigger and softer and takes up to 3 days to work.

Three rules matter more after 60:

1. Each dose goes into a full glass of water, and you drink more through the day.
2. Not if swallowing is difficult: the gel can stick in the throat. See trouble swallowing pills for alternatives.
3. Keep other medicines at least an hour away from it, and don’t take it just before bed.

For frail or older people, the product information for ispaghula husk advises medical supervision, so mention it to your GP or pharmacist.

Magnesium for constipation, and why kidneys matter

Magnesium citrate and magnesium hydroxide are osmotic laxatives: unabsorbed magnesium holds water in the bowel. They work, but part of the magnesium does get into the blood.

The MSD Manual warns that laxatives containing magnesium can harm older adults, people with kidney disease and people on medicines that affect the kidneys. Those include diuretics, ACE inhibitors such as ramipril and ARBs such as losartan. NIH ODS adds that very large doses of magnesium laxatives and antacids, usually over 5,000 mg of magnesium a day, have caused magnesium toxicity, including a death in an older man. The risk rises when the kidneys work less well.

Signs of too much magnesium include low blood pressure, nausea, vomiting, flushing, trouble passing urine and drowsiness, then muscle weakness and an irregular heartbeat. Stop and get medical help if they appear.

Short courses are fine for many people with healthy kidneys. Ask your GP or pharmacist first if you’re over 65 or take any of the medicines above. More in our guides to magnesium citrate for constipation and supplements and kidney disease.

Laxative types in brief

There are four main types of laxative, according to the NHS; magnesium salts belong with the osmotic ones. Pick one to compare:

How quickly each type works, according to the NHS:

• bulk-forming (ispaghula husk): up to 3 days;
• osmotic (macrogol, lactulose): 2–3 days;
• stool softeners (docusate, arachis oil): 12 hours to 3 days;
• stimulant (senna, bisacodyl): 6–12 hours.

General rules from the NHS:

• if you bought a laxative without a prescription, stop when constipation improves and don’t use it for more than 7 days;
• if 3 days of a laxative haven’t helped, speak to a pharmacist or doctor;
• with bulk-forming or osmotic laxatives, drink plenty to avoid dehydration;
• check with a pharmacist first if you have heart failure, difficulty swallowing or take opioid painkillers.

Used too often or for too long, laxatives can cause dehydration, low potassium and, rarely, a bowel blockage.

When to see a doctor: red flags

See a GP if you:

• are constipated and treatment isn’t helping, or it keeps coming back;
• are regularly bloated or have tummy pain;
• notice blood in your poo;
• have lost weight without trying or feel tired all the time;
• notice a sudden change in how you poo;
• take a medicine that causes constipation, such as an opioid painkiller.

Get help quickly if constipation comes with severe tummy pain, vomiting, fever or you can’t pass wind. Lower back pain is on the NIA’s list of these signs too.

One more sign for carers: watery poo leaking in someone who has been constipated can mean faecal impaction, a build-up of hard poo in the rectum. It needs treatment from a GP or nurse, so don’t treat it as ordinary diarrhoea.

How to choose a fibre supplement on iHerb

1. Start with plain psyllium husk, not a “detox” or “cleanse” blend with senna or several herbs.
2. Check the grams of psyllium per serving on the label.
3. Powder is easier to adjust; capsules mean several per dose, which matters if swallowing is hard.
4. Look for sugar or sweeteners if you have diabetes.
5. Treat magnesium as a short-term option only, and only with healthy kidneys.

For everyday supplements after 50, see vitamins for over 50s; for other gut topics, see our gut health section.