Bactrim Side Effects

Nausea, vomiting, diarrhea, and loss of appetite may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including: muscle weakness, mental/mood changes, signs of kidney problems (such as change in the amount of urine, blood in the urine), extreme drowsiness, signs of low blood sugar (such as sudden sweating, shaking, fast heartbeat, hunger, blurred vision, dizziness, or tingling hands/feet).

Get medical help right away if you have any very serious side effects, including: persistent headache, neck stiffness, seizures, slow/irregular heartbeat.

This medication may rarely cause serious (possibly fatal) allergic reactions and other side effects such as a severe peeling skin rash (such as Stevens-Johnson syndrome), blood disorders (such as agranulocytosis, aplastic anemia), liver damage, or lung injury. If you notice any of the following, get medical help right away: skin rash/blisters, itching/swelling (especially of the face/tongue/throat), persistent sore throat or fever, paleness, joint pain/aches, persistent cough, trouble breathing, easy bleeding/bruising, yellowing eyes or skin, persistent nausea/vomiting, unusual fatigue, dark urine.

This medication may rarely cause a severe intestinal condition (Clostridium difficile-associated diarrhea) due to a type of resistant bacteria. This condition may occur during treatment or weeks to months after treatment has stopped. Tell your doctor right away if you develop: persistent diarrhea, abdominal or stomach pain/cramping, blood/mucus in your stool.

Do not use anti-diarrhea or opioid medications if you have any of these symptoms because these products may make them worse.

Use of this medication for prolonged or repeated periods may result in oral thrush or a new yeast infection. Contact your doctor if you notice white patches in your mouth, a change in vaginal discharge, or other new symptoms.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.
  • Clostridioides difficile infection
  • Behcet syndrome
  • goiter
  • hypothyroidism
  • hypoglycemic disorder
  • hyponatremia
  • acidosis
  • megaloblastic anemia
  • glucose-6-phosphate dehydrogenase (G6PD) deficiency anemia
  • hemolytic anemia
  • hemolytic uremic syndrome
  • aplastic anemia
  • hypoprothrombinemia
  • purpura
  • thrombocytopenic disorder
  • agranulocytosis
  • leukopenia
  • granulocytopenic disorder
  • neutropenic disorder
  • eosinophilia
  • methemoglobinemia
  • drug-induced psychosis
  • acute confusion
  • depression
  • cauda equina syndrome
  • peripheral neuropathy
  • Guillain-Barre syndrome
  • periorbital edema
  • tinnitus
  • hearing loss
  • pericarditis
  • myocarditis
  • polyarteritis nodosa
  • vasculitis
  • thrombotic thrombocytopenic purpura
  • pleuritis
  • alveolitis
  • pulmonary infiltrates
  • eosinophilic pneumonia
  • stomatitis
  • glossitis
  • gastroenteritis
  • enterocolitis
  • hepatic necrosis
  • hepatocellular damage
  • hepatitis
  • black tarry stools
  • gastrointestinal hemorrhage
  • interstitial nephritis
  • renal tubular necrosis
  • hematuria
  • skin photosensitivity
  • erythema multiforme
  • toxic epidermal necrolysis
  • Stevens-Johnson syndrome
  • erythema nodosum
  • exfoliative dermatitis
  • pruritus of skin
  • alopecia
  • urticaria
  • lupus-like syndrome
  • arthralgia
  • myelodysplastic syndrome
  • drowsy
  • hallucinations
  • seizure disorder
  • vertigo
  • dizziness
  • insomnia
  • drug fever
  • fatigue
  • chills
  • ataxia
  • skin rash
  • cyanosis
  • anorexia
  • headache disorder
  • dyspnea
  • cough
  • nausea
  • vomiting
  • flatulence
  • diarrhea
  • oliguria
  • proteinuria
  • crystalluria
  • nervousness
  • anaphylaxis
  • angioedema
  • serum sickness
  • paresthesia
  • urolithiasis
  • lethargy
  • intracranial hypertension
  • general weakness
  • acute abdominal pain
  • anuria
  • indifference
  • pancreatitis
  • hypofibrinogenemia

Drug Interactions

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Some products that may interact with this drug include: "blood thinners" (such as warfarin), dofetilide, methenamine, methotrexate.

This product may interfere with certain laboratory tests, possibly causing false test results. Make sure laboratory personnel and all your doctors know you use this product.