For most seniors, an osmotic laxative containing polyethylene glycol (sold as MiraLAX and store-brand equivalents) is the best-supported option. It consistently outperforms other laxative types in clinical trials involving older adults, works within one to three days, and has a strong safety profile for long-term use. But the right choice depends on how severe the constipation is, what other health conditions are in play, and whether simple dietary changes might be enough on their own.
Why Constipation Is So Common After 65
Constipation affects older adults at much higher rates than younger people, and the reasons stack up. The muscles that move stool through the intestines slow down with age. Physical activity tends to drop. Many common medications, including blood pressure drugs, pain relievers, antidepressants, and iron supplements, have constipation as a side effect. Fluid intake often decreases too, especially in people who cut back on drinking to manage bladder issues or simply lose some of the thirst signal that younger people rely on.
All of this means constipation in seniors rarely has a single cause, and the best approach usually combines a good laxative choice with some practical lifestyle adjustments.
Osmotic Laxatives: The Strongest Evidence
Osmotic laxatives work by drawing water into the intestines, which softens stool and makes it easier to pass. Two are widely available over the counter: polyethylene glycol (PEG) and lactulose, which typically requires a prescription.
PEG has the most robust clinical support for seniors. In a trial of older adults, 56% of those taking PEG experienced significant relief of constipation symptoms, compared to just 11% on placebo. A large observational study of 324 patients aged 65 and older (average age 78) found that constipation scores improved significantly within two weeks of starting PEG, and 83% of patients were still using it successfully at one year. That kind of long-term continuation rate signals both that it works and that people tolerate it well.
Lactulose also works. Two randomized trials showed it significantly increases bowel movement frequency and reduces the need for additional laxatives. However, when PEG and lactulose were compared head-to-head over six months, PEG was more effective at relieving symptoms with a similar rate of side effects. PEG also tends to cause less bloating and gas than lactulose, which matters for comfort and compliance.
PEG is a tasteless, odorless powder you mix into any beverage. Most people see results within one to three days.
Stool Softeners: Popular but Weak
Docusate sodium (sold as Colace) is one of the most commonly recommended products for older adults, but the evidence behind it is surprisingly thin. In a study of 40 elderly hospitalized patients, the stool softener group averaged 3.3 bowel movements per week versus 2.5 for placebo, a difference that didn’t reach statistical significance. Patients reported feeling somewhat better overall, but in terms of actually increasing the number of bowel movements, docusate performed only marginally better than a sugar pill.
If constipation is mild and stools are simply hard or uncomfortable to pass, a stool softener might offer some relief. But for chronic or moderate constipation, an osmotic laxative is a much more reliable choice.
Bulk-Forming Laxatives: Effective With a Caveat
Fiber supplements like psyllium (Metamucil), methylcellulose (Citrucel), and calcium polycarbophil (FiberCon) absorb water in the gut and form soft, bulky stool that’s easier to move along. They work well for many seniors and are generally considered very safe.
The critical caveat: they must be taken with plenty of water. Without adequate fluid, bulk-forming laxatives can actually make constipation worse or, in rare cases, cause a blockage. This is a real concern for older adults who already struggle with fluid intake. If you or a family member can reliably drink eight to ten glasses of water a day, a fiber supplement is a reasonable first step. If fluid intake is low or hard to track, an osmotic laxative is the safer bet.
The daily fiber target for adults 51 and older is 22 grams for women and 28 grams for men. Most people fall well short of this through diet alone, which is where supplements can help fill the gap.
Stimulant Laxatives: For Short-Term Use
Stimulant laxatives like senna (Senokot) and bisacodyl (Dulcolax) work by triggering the intestinal muscles to contract. They’re faster-acting than osmotic or bulk-forming options, often producing a bowel movement within 6 to 12 hours. Clinical trials confirm they are more effective than placebo in elderly patients.
These are best used for occasional, short-term relief rather than daily management. Long-term use can lead to the bowel becoming dependent on the stimulation to function, and they carry a higher risk of cramping and electrolyte imbalances than gentler alternatives. For seniors who need something quickly, a stimulant laxative works, but it shouldn’t be the everyday strategy.
Magnesium-Based Products: Watch for Kidney Issues
Milk of magnesia and magnesium citrate are inexpensive, effective osmotic laxatives that many people reach for. For seniors with healthy kidneys, they’re generally fine for occasional use. But the kidneys are responsible for clearing excess magnesium from the body, and kidney function naturally declines with age.
When the kidneys can’t keep up, magnesium builds to dangerous levels in the blood. Older age, reduced kidney function, and long-term use of magnesium-based laxatives are all independent risk factors for this problem. If there’s any history of kidney disease, or if kidney function hasn’t been checked recently, it’s worth choosing a different type of laxative. PEG doesn’t carry this risk because it isn’t absorbed into the bloodstream.
Prunes and Dietary Changes That Actually Help
Before reaching for any over-the-counter product, simple dietary changes can make a meaningful difference. Prunes are the best-studied food for constipation relief. A practical daily dose is six prunes or six ounces of prune juice. Prunes contain sorbitol, a natural sugar alcohol that draws water into the intestines the same way an osmotic laxative does, plus they provide fiber.
Other high-fiber foods that help include beans, lentils, oats, berries, and leafy greens. Increasing fiber intake gradually over a week or two reduces the bloating and gas that come from a sudden jump. Pairing fiber with adequate fluids is essential, as fiber without water can make things worse.
Physical activity, even a daily 15- to 20-minute walk, stimulates intestinal movement and can make a noticeable difference in regularity. For seniors with limited mobility, even gentle seated exercises or abdominal massage can help.
Choosing the Right Option
A practical way to think about this is in tiers. Start with the simplest approaches: more fluids, more fiber through food, daily prunes, and whatever physical activity is manageable. If that’s not enough after a week or two, add a bulk-forming fiber supplement (with plenty of water) or move straight to PEG. Stool softeners can be added alongside either for extra comfort but shouldn’t be relied on alone. Reserve stimulant laxatives for occasional breakthrough constipation when gentler options haven’t worked within a few days.
Constipation that comes on suddenly after age 50, especially with unintentional weight loss, blood in the stool, significant abdominal pain, or a family history of colon cancer, deserves prompt medical evaluation. These can be signs of something beyond ordinary age-related slowing, and a doctor will want to rule out more serious causes before settling on a laxative plan.