Awaiting clinical review. This entry is sourced but has not yet been signed off by a pharmacist or clinician.

Plantago ovata (seed husk)

Psyllium

Psyllium husk works for chronic constipation and modestly lowers LDL cholesterol, and it is the best-supported fibre supplement for both. It probably helps irritable bowel syndrome (IBS) symptoms as part of soluble fibre, and it may lower blood sugar in people who already have type 2 diabetes. The main caution is that it must be taken with plenty of liquid: swallowed dry or with too little fluid it can block the throat, gullet or bowel.

Written by

Healthy and Herbal editorial team

Updated

29 September 2026

Psyllium husk in a bowl with a glass of water

At a glance

Last reviewed 29 September 2026

Evidence

Strong

Best for

Constipation

Typical form & use

Husk powder, about 10 g a day in water

Onset

4+ weeks

Safety

Needs plenty of water; can cause choking or blockage. 5 known interactions, most serious with diabetes medication.

Check with your medications →

What it's used for

Evidence is rated per use. The same ingredient can be strong for one thing and traditional for another.

Use	Evidence	What the research shows
Chronic constipation	Strong	A 2022 meta-analysis of 16 trials (1,251 adults) found 66% of people responded to fibre versus 41% on control (RR 1.48, 95% CI 1.17–1.88), with psyllium showing a significant effect and doses above 10 g a day and at least 4 weeks working best. Results varied a lot between trials, and flatulence was more common on fibre. The EU regulator lists ispaghula husk (psyllium) as a well-established treatment for habitual constipation.^1,7
Lowering LDL cholesterol	Strong	A meta-analysis of 28 trials (1,924 people) found a median of about 10.2 g psyllium a day lowered LDL cholesterol by 0.33 mmol/L (95% CI 0.27–0.38) and apolipoprotein B by 0.05 g/L; the certainty of evidence was moderate for LDL because trials disagreed in size. The EU monograph puts the fall at roughly 7% and notes there are no data on heart attacks or deaths. The US FDA allows a label claim that psyllium husk as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease.^2,7,8
Irritable bowel syndrome	Moderate	A 2014 meta-analysis of 14 trials (906 people) found fibre reduced the chance of staying symptomatic (RR 0.86; number needed to treat 10), with the benefit confined to soluble fibre (RR 0.83; NNT 7) and none from bran. Those pooled trials were not all psyllium. A 2020 network meta-analysis found few IBS trials of soluble fibre, antispasmodics and similar treatments were at low risk of bias, so the certainty is limited. The EU monograph lists psyllium only as an adjuvant in constipation-predominant IBS.^3,5,7
Blood sugar in type 2 diabetes	Limited	A 2015 meta-analysis of 35 trials reported that psyllium taken before meals for several weeks lowered fasting glucose by 37 mg/dL and HbA1c by 0.97 percentage points in people with type 2 diabetes, with little effect in people with normal glucose. Its authors were employed by a psyllium manufacturer, and a 2023 network meta-analysis of soluble fibres in type 2 diabetes ranked galactomannans, not psyllium, most effective. We rate it 2 until independent psyllium-specific reviews confirm it.^4,6

How much

Ranges below are what studies used and what supplements commonly contain. They are not a recommendation for you. Start at the low end.

Constipation (EU monograph)

7–11 g a day, in 1–3 doses^7,1

Husk or husk powder taken with liquid. The 2022 meta-analysis found benefit for stool frequency mainly above 10 g a day and after at least 4 weeks.

Cholesterol (studied)

About 10 g a day^2,7,8

Median dose in the 28-trial meta-analysis of LDL cholesterol. The EU monograph allows 7–20 g a day where more fibre is advisable, under medical supervision for high cholesterol. The FDA claim refers to 7 g or more of soluble fibre from psyllium husk a day.

Fluid with each dose

30 ml of water per 1 g of husk⁷

The EU monograph's minimum, so a 5 g dose needs about 150 ml, plus adequate fluid through the day.

Children 6–12 years

3–8 g a day⁷

For constipation only. The EU monograph does not recommend it under 6, or under 12 for the cholesterol or fibre-adjuvant use.

Timing · Take it during the day, not immediately before bed, and at least half an hour to an hour away from other medicines (EU monograph). The effect on constipation starts 12–24 hours after a dose and sometimes peaks after 2–3 days.With food? · The monograph does not tie it to meals for constipation; the diabetes meta-analysis dosed psyllium before meals. Always mix or swallow it with a full glass of water or other liquid.How long to trial · For constipation the EU monograph says to see a doctor or pharmacist if symptoms last beyond 3 days of use. For stool frequency and cholesterol, the trials behind our ratings ran 3–4 weeks or more, so judge those over about a month.

How people take it

Husk or powder stirred into liquid7–11 g a day for constipationThe form most trials used. Mix with at least 30 ml of liquid per gram and drink straight away, before it thickens. Avoid breathing in the powder.

Capsules or wafersFollow the labelThe EU monograph covers solid dosage forms too, and the same fluid rule applies. Capsules deliver less per piece, so you may need many to reach a trial dose.

Safety

Who should avoid

Difficulty swallowing or throat or gullet problems — choking risk
Bowel blockage, narrowing, megacolon or faecal impaction — do not use
Sudden change in bowel habit over 2 weeks or undiagnosed rectal bleeding
Taking it dry or with too little fluid — can obstruct the throat or bowel
Known allergy to psyllium; regular contact with the powder can sensitise
Opioids and other drugs that slow the gut — only under medical supervision
Debilitated or elderly people — medical supervision advised (EU monograph)

Known interactions

CautionDiabetes medication — The EU monograph says people with diabetes should take psyllium only under medical supervision because their diabetes treatment may need adjusting.

CautionThyroid medication — The EU monograph says use with thyroid hormones needs medical supervision because the thyroid dose may have to be adjusted.

MonitorEpilepsy medication (anticonvulsants) — The EU monograph says absorption of carbamazepine may be delayed, so keep doses half an hour to an hour apart.

MonitorBlood thinners — The EU monograph says psyllium may delay absorption of coumarin anticoagulants, so keep doses half an hour to an hour apart.

MonitorDigoxin & heart-rhythm medication — The EU monograph says absorption of cardiac glycosides such as digoxin may be delayed, so keep doses half an hour to an hour apart.

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Questions people ask

How much water do I need to take with psyllium?

The EU regulator's minimum is 30 ml of liquid for every 1 g of husk, and you should keep drinking fluids through the day. With too little fluid, psyllium can swell and block the throat, gullet or bowel, causing choking, chest pain, vomiting or trouble breathing.

Can psyllium affect my other medicines?

It can delay the absorption of some medicines, including lithium, carbamazepine, digoxin, warfarin-type anticoagulants, and some vitamins and minerals. The EU monograph advises taking it at least half an hour to an hour before or after other medicines. People on diabetes or thyroid treatment should use it under medical supervision because doses may need adjusting.

How long does psyllium take to work?

For constipation, the EU monograph says a dose usually acts within 12–24 hours, sometimes peaking after 2–3 days. A 2022 meta-analysis found stool frequency improved mainly after 4 weeks or more at doses above 10 g a day. Cholesterol trials lasted at least 3 weeks.

Does psyllium lower cholesterol and blood sugar?

It lowers LDL cholesterol modestly, by about 0.33 mmol/L at roughly 10 g a day in a 28-trial meta-analysis, and the US FDA permits a heart-disease health claim for it. Evidence for blood sugar is weaker: one meta-analysis by manufacturer-employed authors found lower fasting glucose and HbA1c in people with type 2 diabetes, but not in people with normal glucose.

Sources

Last reviewed 29 September 2026 · Next review March 2027 · How we rate evidence