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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medically reviewed by WellAlly Editorial TeamLast reviewed October 19, 2026Editorial policy
Medication15 min read

How to Take Cephalexin (Keflex) for Bacterial Skin Infections

Published: October 19, 2026Updated: October 19, 2026

Cephalexin is a common cephalosporin antibiotic prescribed to treat bacterial skin infections such as cellulitis, impetigo, and folliculitis. This guide outlines how to take your medication safely, track your skin's healing progress, manage mild side effects, and recognize when to contact your healthcare provider.

Quick Summary

Take cephalexin at evenly spaced intervals, finish the entire prescribed course even if your skin clears up early, and seek medical care if redness or swelling spreads.

Important Medical Disclaimer

This guide is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult with qualified healthcare providers for medical concerns.

Step-by-Step Guide

1

Follow the Prescribed Dosing Schedule

Take cephalexin exactly as directed by your healthcare provider, usually every 6 or 12 hours depending on your specific formulation. Spacing doses evenly throughout the day maintains a steady concentration of the antibiotic in your bloodstream and skin tissues. You may take cephalexin with or without food, though taking it with a meal or a glass of milk can help reduce mild stomach upset.

2

Complete the Entire Course of Treatment

Continue taking your medication until the entire prescription is finished, which typically lasts between 5 to 10 days. Even if your skin lesion improves or disappears after a few days, bacteria may still linger in deeper tissue layers. Stopping therapy prematurely significantly increases the risk of the infection returning and encourages the development of antibiotic resistance.

Important: Never stop taking cephalexin early without explicit guidance from your prescribing clinician, even if your symptoms have completely resolved.

3

Track the Borders of Your Infection

Use a surgical marker or pen to gently outline the red, inflamed edge of the skin infection when you start the medication. Check the area twice daily in good lighting to verify whether the redness is staying within the line or receding. A slight initial expansion may occur during the first 24 hours, but noticeable improvement in swelling, warmth, and tenderness should be visible by day two or three.

Important: Seek emergency medical care if the redness spreads rapidly past your initial markings, if you develop red streaks traveling toward your heart, or if you develop high fever or chills.

4

Manage Common Gastrointestinal Side Effects

Cephalexin can cause mild side effects such as nausea, indigestion, or loose stools. Staying well-hydrated by drinking plenty of water and eating small, bland meals can alleviate these symptoms. If you decide to take probiotics to support gut health, space them at least two hours away from your cephalexin dose to ensure the antibiotic does not neutralize the beneficial bacteria.

Important: Contact your doctor immediately if you develop severe, watery diarrhea (more than three times per day), severe abdominal cramping, or blood in your stool, as this could indicate a Clostridioides difficile infection.

5

Review Current Medications for Potential Interactions

Inform your pharmacist and clinician about all other prescription drugs, over-the-counter medications, and herbal supplements you take. Cephalexin can interact with medications such as metformin by slowing its clearance from your kidneys, which may increase the risk of low blood sugar. It can also interact with probenecid and certain live vaccines, requiring dosage adjustments or careful monitoring.

6

Store the Medication Appropriately

Store cephalexin tablets or capsules at room temperature between 68°F and 77°F (20°C to 25°C), away from excess moisture, direct light, and heat. Keep the medication tightly closed in its original child-resistant bottle and avoid storing it in humid bathroom cabinets. If you were prescribed oral liquid suspension, keep it refrigerated and discard any unused liquid after 14 days.

Frequently Asked Questions

Can I take cephalexin if I have a penicillin allergy?
It depends on the severity of your allergy. Cephalexin is a cephalosporin antibiotic, which shares a chemical structure with penicillin. While the cross-reactivity rate is low (typically under 2%), you should avoid cephalexin if you have a history of severe, immediate allergic reactions to penicillin, such as anaphylaxis, hives, or airway swelling, unless cleared by an allergist.
How quickly does cephalexin start working on a skin infection?
Most patients notice improvements in pain, localized heat, and swelling within 48 to 72 hours of starting cephalexin. If your infection shows no improvement or continues to worsen after 3 days of therapy, contact your healthcare provider for re-evaluation.
What should I do if I miss a dose?
Take the missed dose as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed one and resume your normal schedule. Never double up on capsules or take two doses at once to make up for a missed one.
Can I drink alcohol while taking cephalexin?
While alcohol does not directly produce a toxic chemical interaction with cephalexin, consuming alcohol can worsen side effects like dizziness, nausea, and dehydration. Alcohol can also suppress your immune response and slow down your body's ability to heal skin tissue.
  1. 1
    Mayo ClinicSource
  2. 2
    National Library of Medicine (MedlinePlus)Source
  3. 3
    NHSSource
  4. 4
    CDCSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed October 19, 2026. · Read our editorial policy