Cephalexin (Keflex): Uses, Dosage, Side Effects & Savings
Cephalexin has been a workhorse antibiotic for over 50 years — safe, affordable, and highly effective for skin infections, UTIs, ear infections, and more. Here is the complete guide.
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A telehealth provider can evaluate your infection and send a prescription to your pharmacy today.
What Is Cephalexin?
Cephalexin is a first-generation cephalosporin antibiotic — part of the beta-lactam family, closely related to penicillin. It kills bacteria by interfering with their cell wall construction. It is especially effective against gram-positive bacteria like Staphylococcus aureus (staph) and Streptococcus (strep), which makes it ideal for skin infections.
Brand name Keflex was once widely used; today, generic cephalexin has almost entirely replaced it. It comes in 250 mg and 500 mg capsules and as a suspension for children.
What Does Cephalexin Treat?
| Infection Type | Why Cephalexin? |
|---|---|
| Skin and soft tissue infections — cellulitis, impetigo, wound infections | Excellent coverage of staph and strep — the main culprits |
| Urinary tract infections (UTIs) | Effective against E. coli and other common uropathogens |
| Strep throat / pharyngitis | Good alternative to amoxicillin; used in mild penicillin-sensitive patients |
| Ear infections | Second-line option |
| Bone infections (osteomyelitis) | Used for oral step-down therapy after IV antibiotics |
| Dental infections | Alternative to amoxicillin for dental prophylaxis |
Dosage
- Mild-moderate infections: 250–500 mg every 6 hours (4x daily) or 500 mg every 12 hours (2x daily)
- Severe infections: Up to 1,000 mg every 6 hours
- Strep throat: 500 mg twice daily for 10 days
- UTIs: 500 mg twice daily for 7 days
📌 Take with or without food
Cephalexin can be taken with or without food. If it upsets your stomach, take it with a meal. Space doses as evenly as possible throughout the day and complete the full course even if you feel better early.
Side Effects
- Diarrhea, nausea, vomiting, stomach pain — the most common complaints
- Rash — mild rash is common; severe rash means stop and call your doctor
- Yeast infections
- Headache, dizziness — less common
🚨 Stop immediately and seek care if you experience:
- Severe skin reaction (blistering, peeling)
- Swelling of face, tongue, or throat
- Difficulty breathing
- Severe or persistent diarrhea (possible C. difficile)
Frequently Asked Questions
Is cephalexin the same as Keflex?
Yes. Keflex is the original brand name for cephalexin. The brand is rarely dispensed today; generic cephalexin is the standard at all pharmacies. The medication is identical.
Can I take cephalexin if I am allergic to penicillin?
Possibly. The cross-reactivity rate between penicillins and first-generation cephalosporins is estimated at 1–2% for true allergy. If your penicillin allergy was mild (e.g., a rash), many providers will still prescribe cephalexin. If your reaction was severe (anaphylaxis, throat swelling, breathing difficulty), your provider will likely choose a completely different antibiotic class.
How long does it take for cephalexin to work on a skin infection?
Most skin infections show improvement within 48–72 hours on cephalexin. Redness, warmth, and swelling should begin to reduce. If your infection is spreading — the redness is expanding, you are developing a fever, or you feel more unwell — contact your provider promptly as you may need IV antibiotics or drainage of an abscess.
Can I get cephalexin prescribed online?
Yes. Skin infections, UTIs, and strep throat can often be evaluated via telehealth. A licensed provider will ask about your symptoms, review any photos (for skin infections), and send a prescription to your pharmacy the same day if appropriate.
How much does cephalexin cost without insurance?
Generic cephalexin is very affordable — typically $4–$15 for a standard course with a free Rx.com discount card. It is on most pharmacy $4 generic lists. See current prices at /drug/cephalexin.
Is cephalexin used for MRSA?
No. Standard cephalexin (and most cephalosporins) is NOT effective against MRSA (methicillin-resistant Staphylococcus aureus). If your skin infection does not improve on cephalexin, or if MRSA is suspected, your provider may switch you to trimethoprim-sulfamethoxazole (Bactrim), doxycycline, or clindamycin — all of which have MRSA activity.
Get a Cephalexin Prescription Online
Skin infections, UTIs, and more — a licensed provider can evaluate your symptoms and send your prescription today.