Keflex Dosages: Your GoodRx Guide
Key takeaways:
Keflex (cephalexin) is a prescription antibiotic for kids and adults. It comes as a capsule, tablet, and oral liquid, and most people take 2 to 4 doses per day for up to 7 to 14 days.
If you or a loved one have moderate or severe kidney problems, you’ll likely take Keflex at a lower dose and/or less often throughout the day.
Keflex is available as a lower-cost generic. GoodRx can help you save over 55% off the average retail price at certain pharmacies.
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Table of contents
Antibiotics are the best way to treat a bacterial infection. And if you have an infection in your lungs, ears, or skin, your healthcare provider may narrow down the best antibiotic to Keflex (cephalexin). It’s an effective and affordable medication for many people.
While name-brand Keflex is no longer marketed in the U.S., its generic equivalents are widely available at pharmacies across the country.
If your healthcare provider recommends it as the best option for your infection, it’s important to know how to take it. Knowing your Keflex dosage is no exception.
What’s the typical Keflex dosage for adults?
Keflex is an oral medication that comes in a few shapes and sizes. An oral capsule is the most common version, but a tablet and suspension (liquid) are also available. The capsules and tablets generally contain 250 mg or 500 mg of cephalexin, but a 750-mg capsule also exists. The oral suspension is filled at concentrations of 125 mg/5 mL and 250 mg/5 mL.
There are two go-to Keflex dosages for adults. One option is taking 250 mg 4 times per day for 7 to 14 days (1 to 2 weeks). Another option is taking 500 mg only twice per day for the same timeframe. You can take your Keflex doses with or without food.
But, if your infection is more severe, you may be told to take up to 4 g (4,000 mg) in a given day. You’ll still want to break up this amount into 2 to 4 smaller doses throughout the day.
What’s the typical Keflex dosage for children?
Kids as young as 1 year old are eligible to take Keflex. Keflex dosages for teens ages 15 and older are the same as those in adults. Keflex dosages for children under 15 years old are personalized based on body weight. And among younger kids who have trouble swallowing pills, the oral suspension is a popular option.
Depending on your child’s body weight and type of infection, they’ll likely receive Keflex at a dosage of 25 to 50 mg per kilogram of body weight per day.
For ear infections, they may take up to 100 mg per kg. Like adults, these dosages are split up into smaller doses throughout the day and last for about 7 to 14 days.Â
For example, if your child weighs 22 lbs (10 kg) and is prescribed Keflex 50 mg per kilogram, they’d take 500 mg of medication per day. This could be divided into four smaller 5 mL (125 mg) liquid doses. Heavier body weights generally take larger doses.
Note: If your child is 11 months or younger and needs an antibiotic, Keflex may not be the best choice.
Are there any dosage adjustments for medical conditions?
If you have kidney problems, you may be prescribed a lower Keflex dosage. Keflex leaves your body through your kidneys, so if they aren’t working as well as they could, the medication could build up and lead to extra side effects.
To make up for this, a lower Keflex dosage makes your prescription safer and more tolerable.
If you’re an older adult or have been told you have liver problems, there aren’t any special dosing adjustments to keep in mind.
Dosage for people with kidney problems
If your kidney problems are mild, you can generally take a standard dose of Keflex. But if they’re more severe, adjustments may be necessary.
If you have moderate or severe kidney problems, the recommended Keflex dose is based on your creatinine clearance (CrCl). This is a standard lab measurement used to predict kidney health — a lower CrCl number means less efficient kidneys.
But you can’t figure out your CrCl on your own, so your healthcare provider will help find it out for you.
| Kidney status | Recommended Keflex dose |
|---|---|
| Healthy kidneys | No adjustment needed |
| Mild kidney problems | No adjustment needed |
| CrCl between 30–59 mL/minute | No adjustment needed, but try to stay under 1 gram (1,000 mg) per day |
| CrCl between 15–29 mL/minute | 250 mg 2–3 times daily |
| CrCl between 5–14 mL/minute | 250 mg once daily |
| CrCl between 1–4 mL/minute | 250 mg every other day |
If you’re receiving dialysis, your kidney specialist can tell you if you should time your Keflex doses with your dialysis sessions.
Drug interactions
It’s not common, but a few medications can affect your Keflex dosage. This is generally the case if you take another medication that affects your kidneys in a meaningful way. Probenecid, a gout medication, is one example.
Keflex interactions are discussed more in another GoodRx article.
What happens if you miss a dose of Keflex?
It’s easy to forget a Keflex dose every now and then, especially since most people take multiple doses per day. With a hectic schedule, it’s possible for a dose to slip through the cracks.
If this happens to you, no need to panic. Take the missed Keflex dose as soon as you remember. But if it's almost time for your next dose, skip the missed dose and take your next dose at the normal scheduled time. No need to double up doses to make up for a missed one.
But, still try your best to avoid missing Keflex doses. Multiple missed doses can affect the antibiotic’s effectiveness. This could lead to an undertreated infection and possible antibiotic resistance — this can cause trouble down the road.
Make sure to loop in your pharmacist if you find yourself often missing doses.
What should you do if you take too much Keflex?
At normal doses, Keflex can cause side effects like nausea, diarrhea, and stomach pain. Taking too much Keflex can enhance these side effects.
Reported cases of Keflex overdose have included new or worsening nausea, vomiting, or diarrhea. Pain in the upper abdomen and bloody urine have also been reported.
If you think you’ve taken too much Keflex, make sure to contact your healthcare provider right away. A Keflex antidote isn’t available, so they can talk to you about how to approach the situation.
In most cases, they’ll recommend supportive care tips that aim to address possible symptoms you’re experiencing. Contacting Poison Control at 1-800-222-1222 is another option.
Still, make sure to listen to your body. If your symptoms feel severe, it’s better to go to the nearest emergency room right away.
How to save on Keflex
There are many ways to save on Keflex, which is available as a generic medication. GoodRx can help you save over 55% off the average retail price. Generic cephalexin’s price at certain pharmacies is as low as $10.68 with a free GoodRx discount.
The bottom line
Keflex is an oral antibiotic that treats bacterial infections. It’s common for adults and teens ages 15 years and older to take one 250 or 500 mg capsule 2 to 4 times per day for 7 to 14 days. Children’s Keflex dosages are based on body weight. People with moderate or severe kidney problems generally take lower doses of Keflex.
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References
Advanced RX Pharmacy of Tennessee, LLC. (2021). Cephalexin [package insert].
MedlinePlus. (2016). Cephalexin.
National Kidney Foundation. (n.d.). Creatinine.
National Kidney Foundation. (n.d.). Dialysis.
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