Other Name(s):

Amorphophallus konjac, Amorphophallus rivieri, Glucomanano, Glucomannane, Konjac, Konjac Mannan.


Glucomannan is a sugar made from the root of the konjac plant (Amorphophallus konjac). Glucommanan powder, capsules, and tablets are used as medicine.

Glucomannan is used for constipation, weight loss in adults and children, type 2 diabetes, blood sugar control, and lowering cholesterol.

In foods, glucomannan is used as a thickener or gelling agent. Glucommanan flour and powder are used in food.

How does it work?

Glucomannan might work in the stomach and intestines by absorbing water to form a bulky fiber which treats constipation. It may also slow the absorption of sugar and cholesterol from the gut, helping to control sugar levels in diabetes, and reducing cholesterol levels.


Diabetes: What Raises and Lowers Your Blood Sugar Level? See Slideshow

Uses & Effectiveness

Possibly Effective for...

  • Constipation. Research suggests that taking glucomannan by mouth can relieve constipation in children and adults.
  • Diabetes. Taking glucomannan by mouth seems to reduce cholesterol, blood sugar levels, and blood pressure in people with diabetes.
  • High cholesterol. Taking glucomannan by mouth seems to improve cholesterol levels in people with high cholesterol, with or without diabetes.

Insufficient Evidence to Rate Effectiveness for...

  • Stomach condition called dumping syndrome. Some early research suggests that taking a specific glucomannan product (Propol, Pharmacia, Woerden, The Netherlands) reduces the risk of blood sugar becoming too low after eating in people who have had stomach surgery. However, not all research agrees. Some research suggests that glucomannan does not improve blood sugar absorption in children after stomach surgery.
  • High blood pressure. Some early research suggests that glucomannan might improve blood pressure in people with high blood pressure.
  • Overactive thyroid (hyperthyroidism). Early research suggests that glucomannan plus methimazole and propranolol reduce thyroid hormone levels in people with too much thyroid hormone in the body.
  • Obesity. There is early research that suggests taking glucomannan by mouth might improve weight loss in overweight and obese adults and children. However, not all research agrees.
  • Other conditions.
More evidence is needed to rate glucomannan for these uses.

Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, and Insufficient Evidence to Rate (detailed description of each of the ratings).

Side Effects

Glucomannan powder or flour is LIKELY SAFE when consumed as food. Glucomannan powder and capsules are POSSIBLY SAFE for most adults and children when used in medicinal amounts for up to 4 months. However, solid tablets containing glucomannan are POSSIBLY UNSAFE for adults and LIKELY UNSAFE for children. These can sometimes cause blockages of the throat or intestines.


Diabetes is defined best as... See Answer

Special Precautions & Warnings

Pregnancy and breast-feeding: There is not enough reliable information about the safety of taking glucomannan if you are pregnant or breast-feeding. Stay on the safe side and avoid use.

Diabetes: Glucomannan may interfere with blood sugar control. Monitor blood sugar closely if you have diabetes and use glucomannan.

Surgery: Glucomannan might interfere with blood sugar control during and after surgery. Stop using glucomannan at least 2 weeks before a scheduled surgery.


Medications for diabetes (Antidiabetes drugs)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.

Glucomannan can decrease blood sugar in people with type 2 diabetes. Diabetes medications are also used to lower blood sugar. Taking glucomannan along with diabetes medications might cause your blood sugar to go too low. Monitor your blood sugar closely. The dose of your diabetes medication might need to be changed.

Some medications used for diabetes include glimepiride (Amaryl), glyburide (DiaBeta, Glynase PresTab, Micronase), insulin, pioglitazone (Actos), rosiglitazone (Avandia), chlorpropamide (Diabinese), glipizide (Glucotrol), tolbutamide (Orinase), and others.

Medications taken by mouth (Oral drugs)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.

Glucomannan absorbs substances in the stomach and intestines. Taking glucomannan along with medications taken by mouth can decrease how much medicine your body absorbs, and decrease the effectiveness of your medication. To prevent this interaction, take glucomannan at least one hour after medications you take by mouth.


The following doses have been studied in scientific research:


  • For type 2 diabetes with high cholesterol: 3.6 to 10.6 grams of glucomannan per day.

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