Cephalexin

1st-gen Cephalosporin

Also sold as Keflex

Onset of effect

1 hr – 2 hr

Felt/clinical effect

Tmax (peak blood level)

1 hr – 2 hr

Pharmacokinetic peak

Duration of effect

6 hr – 8 hr

Per single dose

Effect timeline

Approximate single-dose timeline. Onset shows when effects are felt; Tmax shows when blood levels peak.

2 hr4 hr6 hr

Onset of effectTmax (peak blood level)Wears off

Notes

Q6H dosing for skin/soft tissue.

What this is

Cephalexin is a 1st-gen cephalosporin given by the oral route. It's typically used in the antibiotic category.

What the numbers mean

After one oral dose you'd typically start noticing the effect in 1 hr – 2 hr. The drug reaches its highest blood level in about 1 hr – 2 hr, and a single dose usually keeps working for around 6 hr – 8 hr.

Practical tips

Swallow with water; check the label for food restrictions. Finish the full course even if you feel better.

Important

Don't combine with other products in the same drug class without checking with a pharmacist. Stop and seek medical advice if you have an unexpected reaction, severe side effect, or symptoms that don't improve.

All timings are approximate population ranges for a typical adult dose. Individual response varies with age, genetics, formulation, food, and other medications.

Typical dosing

Source: OpenFDA drug label · adult dosing unless noted

Doses vary by age, weight, kidney/liver function, and indication. Don't change your dose without talking to your prescriber.

Verify on the exact label used:DailyMed search·OpenFDA record

Side effects & warnings

Source: OpenFDA drug label

Verify on the exact label used:DailyMed search·OpenFDA record

Educational information only — not medical advice. Times vary by person, dose, and formulation. Always consult a doctor or pharmacist for personal guidance.