Compare Keflex vs. Flagyl

Head-to-head comparisons of medication uses, side effects, ratings, and more.

Keflex (cephalexin)

Prescription only

Flagyl (metronidazole)

Prescription only
Treats bacterial infections.

Keflex (cephalexin) is good for treating many bacterial infections, and is available as a generic.

3.7/ 5 average rating with 686 reviewsforKeflex
Treats and prevents bacterial infections.

Flagyl (metronidazole) is very good at treating certain bacterial infections, but you can't have any alcohol while on it since it'll make you throw up a lot.

Upsides
  • Available in generic.
  • Available in different forms: tablet, capsule, and suspension.
  • Used to treat many types of bacterial infections.
  • Can be taken with or without food.
  • Generally few side effects compared with other antibiotics.
  • Flagyl (metronidazole) is good at killing a variety of bacteria.
  • Unlike many other antibiotics, Flagyl (metronidazole) is less likely to make bacteria resistant to it.
  • Most forms are available as a generic, so it's relatively cheap.
Downsides
  • Can cause diarrhea.
  • You may need to take Keflex (cephalexin) 2 to 4 times a day, which can be hard to remember.
  • If you're allergic to penicillins or other antibiotics, you might not be able to take this medicine.
  • You can't drink alcohol while on Flagyl (metronidazole), and for at least 3 days after you finish it.
  • Side effects can include nausea, headache, stomach upset, and a metallic taste in your mouth.
  • If you're taking Flagyl (metronidazole) for a long time, there's a risk of more side effects, such as nerve damage.
  • If you're on blood thinners, let your doctor know. Flagyl (metronidazole) can interact with your medicines and make you more likely to bleed.
Used for
Dosage forms
  • Pill
  • Liquid
  • Pill
  • Extended-release pill
  • Injection
Price
Want to save even more money?
Sign up now for a 30-day trial and save up to 95% at CVS, Kroger, Albertsons, and other pharmacies.
Reviews
686 reviews so far
64%
saidit'sworth it
48%
saiditworked well
14%
saidit'sa big hassle

Have you used Keflex (cephalexin)?

Leave a review
Not enough review data.Leave a review
Side effects
The Keflex (cephalexin) FDA package insert doesn’t have numbers about how common side effects are.
13possible side effects
  • Headache
    18%
  • Nausea
    10%
  • Metallic taste
    9%
  • Genital itching
    5%
  • Dizziness
    4%
  • Diarrhea
    4%
  • Stomach problems
    4%
  • Overgrowth of yeast
    3%
  • Stuffy nose
    3%
  • Menstrual cramps
    3%
  • Abnormal urine
    3%
  • Dry mouth
    2%
  • Urinary tract infection
    2%
See more detailed side effects
Risks and risk factors
  • Diarrhea
  • New infections while taking Keflex (cephalexin)
    • Weakened immune system
    • Not taking Keflex (cephalexin) correctly
  • Allergic reaction
    • History of penicillin or cephalosporin allergies
See more detailed risks and warnings
  • Seizure or brain problems
    • Taking high doses of Flagyl (metronidazole)
    • Taking Flagyl (metronidazole) for a long time
  • Nerve damage
    • Taking high doses of Flagyl (metronidazole)
    • Taking Flagyl (metronidazole) for a long time
  • Cancer
  • New infection while taking Flagyl (metronidazole)
    • Taking Flagyl (metronidazole) incorrectly
  • Interaction with alcohol
    • Drinking alcohol while taking Flagyl (metronidazole)
See more detailed risks and warnings