Psyllium is a soluble, gel-forming fiber from the husk of Plantago ovata seeds. It is a bulk-forming laxative used to treat constipation: it absorbs liquid in the gut, swells and forms a softer, bulkier stool. It is also used as a fiber supplement and has been studied for cholesterol and blood sugar.
Also known as: psyllium husk, ispaghula, Metamucil.
Psyllium comes as powder, granules, capsules and wafers, usually taken one to three times a day as the package directs (MedlinePlus). The FDA heart-health claim for psyllium is based on 7 g or more a day of soluble fiber from psyllium husk, and a 2018 meta-analysis of cholesterol trials (Jovanovski) used a median of about 10.2 g of psyllium a day. These are study protocols, not a recommendation.
Psyllium is sold both as an over-the-counter bulk laxative (Metamucil, Konsyl and others) and as a fiber supplement. FDA allows foods with psyllium husk to carry a health claim that soluble fiber from psyllium, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease (21 CFR 101.81).
MedlinePlus says to mix powder or granules with 8 ounces (240 mL) of liquid right before use, and that you must drink at least that much liquid with each dose for it to work and to prevent side effects; call a doctor for trouble swallowing or breathing, stomach pain, nausea or vomiting. Do not take digoxin, aspirin or nitrofurantoin within 3 hours of psyllium, and do not use it for constipation longer than 1 week without a doctor's advice. In studies, psyllium lowered LDL cholesterol (Jovanovski 2018, 28 trials) and improved fasting blood sugar and HbA1c in people with type 2 diabetes, with little effect in people with normal blood sugar (Gibb 2015).
Psyllium is not absorbed into the blood; it works inside the gut, so it has no half-life or time to peak.
How Dose Track handles peptides · Reconstitution calculator · Half-life calculator