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Common Brand Name: Keflex

Side Effects and Precautions

Medically reviewed by Jessica Swirble, PharmD
Last updated on March 16, 2024

Drug Information | Side Effects | Use & Dosage | Request a Prescription

What are the side effects of cephalexin?

The use of cephalexin has been shown to cause side effects in some patients.

Common mild side effects of cephalexin use include:

  • Diarrhea
  • Nausea
  • Vomiting
  • Stomach pain
  • Indigestion
  • Vaginal itching or discharge

More severe side effects include:

  • Severe diarrhea
  • Diarrhea with blood in it
  • Rash
  • Hives
  • Itching
  • Difficulty breathing or swallowing
  • Swelling
  • Lightheadedness or shortness of breath
  • Seizures
  • Fever or chills
  • Dark-colored urine
  • Yellowing of the skin or eyes
  • Unexplained bleeding or bruising

Seek medical attention immediately if you experience any severe symptoms while taking cephalexin. If you experience mild side effects that become severe or do not go away after a few days, speak to a healthcare provider right away.

What should I tell my healthcare provider before using cephalexin?

Tell your healthcare provider about any existing medical conditions, allergies, or other medications you are taking before starting treatment with cephalexin. This includes prescription drugs, over-the-counter medications, and dietary supplements, as they may interact with this drug.

Tell your provider if you are taking these medications or supplements:

  • Anticoagulants
  • Metformin
  • Probenecid
  • Diuretics
  • Zinc supplements
  • Oral contraceptives

You should also mention medical conditions such as:

  • Allergies to cephalosporin or penicillin antibiotics
  • Allergies
  • Kidney disease
  • Liver disease
  • Gastrointestinal problems or GI disease
  • Vitamin K deficiency

If you are pregnant, planning to become pregnant, or breastfeeding, consult your healthcare provider before using cephalexin to assess potential risks and benefits.

Are there any other special instructions I should follow?

You can follow your regular diet while taking cephalexin. Talk to your healthcare provider about the use of this drug with food, beverages, alcohol, and tobacco.

Your healthcare provider will tell you if you should avoid certain foods, beverages, or products while using cephalexin. It is extremely important to follow their guidance, as certain drugs can interact with other substances in the body---leading to potentially severe reactions. If you have any questions about special instructions you should follow while taking this drug, talk to your healthcare provider before use.

What should I do in case of an overdose?

The symptoms of a cephalexin overdose include:

  • Nausea
  • Vomiting
  • Severe or bloody diarrhea
  • Pink, red, or dark-colored urine
  • Stomach pain

If you experience any of these symptoms, call the poison control helpline at 1-800-222-1222. If an individual has collapsed, is having seizures, or is unresponsive, call 9-1-1 immediately.

Medically reviewed by Jessica Swirble, PharmD on March 16, 2024