Fibre

Glucomannan

Also called: konjac, konnyaku

A soluble fibre from konjac root that swells in water.

Why people take it
Weight loss, constipation, cholesterol.
What the evidence says
Small cholesterol benefits; little weight loss.
How it is usually taken
Usually 1 g with a full glass of water 30 minutes before meals, up to three times a day; tablets can cause choking without enough water.
Be careful
Tablets have caused choking and blockage; always take with plenty of water.
Medicines it can interact with
Slows absorption of other medicines (take 2 hours apart); may lower sugar.

Other fibre

PsylliumInulinMethylcelluloseWheat dextrinPartially hydrolysed guar gumBeta-glucanApple cider vinegar

Common questions

What is Glucomannan?

A soluble fibre from konjac root that swells in water.

Why do people take Glucomannan?

Weight loss, constipation, cholesterol.

Does Glucomannan work?

Small cholesterol benefits; little weight loss.

How much Glucomannan do people take?

Usually 1 g with a full glass of water 30 minutes before meals, up to three times a day; tablets can cause choking without enough water.

Is Glucomannan safe?

Tablets have caused choking and blockage; always take with plenty of water.

Does Glucomannan interact with medicines?

Slows absorption of other medicines (take 2 hours apart); may lower sugar.

Sources and further reading

Last reviewed 31 October 2026. Written by Satya Babu.

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For information only, not medical advice. Supplements are not medicines: they are not tested and approved like drugs before they are sold, and they can interact with medicines. Talk to your doctor or pharmacist before you start one, especially if you are pregnant or breastfeeding, take regular medicines, or have kidney, liver or heart disease.