Background

Black psyllium comes from the seed husks of the Plantago arenaria plant. It contains high amounts of soluble dietary fiber.

Black psyllium adds bulk to the stool which might help with constipation, diarrhea, and irritable bowel syndrome (IBS). It also controls how quickly sugars are absorbed from the gut, which might help control blood sugar levels in people with diabetes.

People commonly use black psyllium for treating and preventing constipation. It is also used for diarrhea, obesity, diabetes, high blood pressure, and many other conditions, but there is no good scientific evidence to support most of these uses.

Don't confuse black psyllium with blond psyllium. These are not the same.

Safety Safety definitions

When taken by mouth: Black psyllium is likely safe when consumed with plenty of water. Drink at least 8 ounces of fluids for every 3-5 grams of husk or 7 grams of seed. Mild side effects include bloating and gas. In some people, black psyllium can cause allergic reactions.

Black psyllium is likely unsafe when consumed without enough water. It might cause choking or block the gastrointestinal (GI) tract.

Special Precautions & Warnings:

Pregnancy and breast-feeding: Taking black psyllium during pregnancy or breast-feeding seems to be safe, as long as enough fluids are taken with each dose.

Gastrointestinal (GI) disorders: Don't use black psyllium if you tend to develop hard stools in the rectum due to GI tract narrowing, or have a condition that can lead to obstruction, such as spastic bowel.

Phenylketonuria: Some black psyllium products might be sweetened with aspartame (NutraSweet). If you have phenylketonuria, avoid these products.

Swallowing disorders: Do not use black psyllium if you have problems swallowing. Black psyllium might increase your risk of choking.

Effectiveness

Dosing & administration

Black psyllium has most often been used by adults in doses of 10-30 grams by mouth, in 1-3 divided doses daily, for up to 6 months. Always drink at least 8 ounces of fluids for every 3-5 grams of husk or 7 grams of seed. Speak with a healthcare provider to find out what type of product and dose might be best for a specific condition.

Interactions with pharmaceuticals

Carbamazepine (Tegretol)

Interaction Rating=Moderate Be cautious with this combination.

Black psyllium contains large amounts of fiber. Fiber can decrease how much carbamazepine the body absorbs. This might decrease the effects of carbamazepine.

Digoxin (Lanoxin)

Interaction Rating=Minor Be watchful with this combination.

Black psyllium is high in fiber. Fiber can decrease how much digoxin the body absorbs. This might decrease the effects of digoxin.

Ethinyl estradiol

Interaction Rating=Minor Be watchful with this combination.

Ethinyl estradiol is a form of estrogen. Psyllium can decrease how much ethinyl estradiol the body absorbs. But it is unlikely that this will reduce the effects of ethinyl estradiol.

Lithium

Interaction Rating=Moderate Be cautious with this combination.

Black psyllium contains large amounts of fiber. Fiber can decrease how much lithium the body absorbs. This might decrease the effects of lithium. To avoid this interaction, take black psyllium at least 1 hour after lithium.

Medications taken by mouth (Oral drugs)

Interaction Rating=Minor Be watchful with this combination.

Black psyllium contains large amounts of fiber. Fiber can decrease, increase, or have no effect on how much medicine the body absorbs. Taking black psyllium along with medicine you take by mouth can impact the effects of your medicine. To prevent this interaction, take black psyllium 30-60 minutes after medications you take by mouth.

Metformin (Glucophage)

Interaction Rating=Moderate Be cautious with this combination.

Black psyllium contains large amounts of fiber. The fiber in psyllium might increase how much metformin the body absorbs. This might increase the effects of metformin. To avoid this interaction, take black psyllium 30-60 minutes after medications you take by mouth.

Olanzapine (Zyprexa)

Interaction Rating=Moderate Be cautious with this combination.

Black psyllium contains large amounts of fiber. Fiber can decrease how much olanzapine the body absorbs. This might decrease the effects of olanzapine.

Interactions with herbs & supplements

Iron: Taking black psyllium with iron supplements can reduce the amount of iron that the body absorbs. To avoid this interaction, take iron supplements one hour before or four hours after black psyllium.
Riboflavin: Psyllium seems to slightly reduce the amount of riboflavin that the body absorbs. But this probably isn't a big concern.

Interactions with foods

Taking psyllium can make it difficult to digest fat from the diet. This can increase the amount of fat lost in the stool. Taking psyllium with meals over a long period of time might also affect nutrient absorption. In some cases, it might be necessary to take vitamin or mineral supplements.