Warnings

Colesevelam

Medically Reviewed by Dr. Harshi Dhingra, M.D.

Last Reviewed: May 29, 2025

Warnings

Colesevelam (WelChol) Risks, Warnings, and Complications

Colesevelam can cause or worsen health problems in certain people. Talk to your doctor or pharmacist about other treatment options for high cholesterol or high blood sugar if you are at increased risk of adverse reactions from this drug. Some of the risks of taking colesevelam include:

HYPERTRIGLYCERIDEMIA AND PANCREATITIS: Taking colesevelam (or other bile acid sequestrants) can lead to an elevation in blood triglyceride levels, which can lead to pancreatitis (inflammation of the pancreas). In people with type 2 diabetes, a greater increase in blood triglyceride levels occurs when colesevelam is used alone compared to when colesevelam is used in combination with other diabetes medicines such as pioglitazone, sulfonylureas, and insulin.
Your doctor will do a lipid panel to check blood levels of triglycerides before prescribing colesevelam and periodically while you are on this drug. People who have a triglyceride level above 500 mg/dL or those who have had pancreatitis induced by high lipid levels (high triglycerides) in the past should not take colesevelam. Those with TG levels above 300 mg/dL may experience a greater increase in colesevelam and require additional monitoring.
Seek immediate medical attention if you develop symptoms of acute pancreatitis on colesevelam, such as severe stomach pain with or without nausea and vomiting.
GASTROINTESTINAL OBSTRUCTION: There are postmarketing reports of intestinal blockage in people taking colesevelam. This medication is not recommended in people with gastroparesis (paralysis of the stomach), other gastrointestinal motility disorders, previous major surgery on the digestive system, or a previous history of bowel obstruction. Seek prompt medical attention for symptoms of bowel obstruction, such as severe abdominal pain or severe constipation.
DYSPHAGIA OR ESOPHAGEAL OBSTRUCTION: Due to the large tablet size, colesevelam tablets can cause dysphagia (trouble swallowing) or esophageal obstruction. People who have difficulty swallowing tablets should use other drug forms such as the suspension or chewable bars.
VITAMIN DEFICIENCIES: Colesevelam can decrease the body’s ability to absorb nutrients, specifically fat-soluble vitamins (vitamins A, D, E, and K). This risk is higher in people who are at a risk of vitamin K deficiency, for example, those taking blood thinners such as warfarin or those with GI malabsorption syndromes. If you take oral vitamin supplements, make sure you take them at least 4 hours before your colesevelam dose.
DRUG INTERACTIONS: Colesevelam can decrease the absorption of certain medicines from the gut. Follow your doctor’s instructions carefully in terms of timing of your medicines. You may need to take certain drugs with known interactions or a narrow therapeutic index at least 4 hours before your colesevelam dose.
RISK IN PHENYLKETONURIA (PKU): Each 3.75-gram packet of colesevelam powder for oral suspension contains 27 mg of phenylalanine. This substance can cause brain damage in people with an inherited condition called phenylketonuria (PKU).

Precautions Before Starting Colesevelam (WelChol)

Tell your doctor if you have ever had an allergic reaction to colesevelam, any of the active or inactive ingredients in colesevelam formulations, other cholesterol-lowering medications, or any other medications. Your pharmacy can give you a list of ingredients.

Give your doctor and pharmacist a complete list of your medications, including prescription drugs, over-the-counter medicines, vitamins, supplements, and herbal products. This can help avoid possible interactions between your medications.

Give your doctor a complete medical history. Colesevelam may not be safe for people with certain medical conditions such as bowel blockage, high triglycerides, pancreatitis, gastrointestinal surgery, malabsorption syndromes, gastroparesis, dysphagia (difficulty swallowing), or phenylketonuria.

Tell your doctor if you are pregnant, might be pregnant, or planning a pregnancy soon. Also, tell your doctor if you are nursing an infant on breast milk.

Precautions During Use of Colesevelam (WelChol)

Keep all your medical and lab appointments while on colesevelam. Your doctor may order blood tests to check serum triglyceride levels before starting treatment and periodically while you are on colesevelam.

Eat a special diet (low-cholesterol, low-fat diet) while on colesevelam and get regular exercise. These lifestyle changes can help you get the best results from this medication.

Tell all your healthcare providers you are on colesevelam, including before dental treatments.

Call your doctor if you become pregnant while taking this medication.

Colesevelam (WelChol) Drug Interactions

Certain other drugs can affect how colesevelam works. Possible interactions between colesevelam and other medicines can increase the risk of severe side effects. Your doctor may change your dose, switch you to a different medication, or monitor you closely for adverse effects if there are known interactions between colesevelam and your other medications.

If you are on the following medications, take them at least 4 hours before you take colesevelam:

Immunosuppressant cyclosporine (Neoral, Gengraf, Sandimmune)
Thyroid medicine levothyroxine (Synthroid)
Diabetes medicines glimepiride (Amaryl), glipizide (Glucotrol), and glyburide (Diabeta)
High blood pressure drug olmesartan (Benicar)
Oral contraceptives (birth control pills)
Antiepileptic drug phenytoin (Dilantin)
Vitamins A, D, E, and K

The above list does not include all the possible interactions of colesevelam. Give your healthcare professional a complete list of your medications, including prescription drugs, over-the-counter medications, dietary supplements, and herbal remedies. Also, tell your doctor or pharmacist if you smoke, drink alcohol, or use recreational drugs because some of these substances can cause serious health complications when used with prescription medications.

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