Drug & supplement interaction

Hydroxymethylbutyrate (hmb) + Cephalexin

Cephalexin brand names: Keflex, Keftab, Cephalex, Lexin.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 20, 2026
The bottom line No known interaction

We found no known interaction between Hydroxymethylbutyrate (hmb) and Cephalexin in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Hydroxymethylbutyrate (hmb) and Cephalexin

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Cephalexin and Hydroxymethylbutyrate (hmb) in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

Worth understanding: our licensed dataset holds no drug-interaction record for Hydroxymethylbutyrate (hmb) at all — not against Cephalexin, and not against any other medication we track. This verdict therefore rests on the absence of any recorded data, not on research that looked at this combination and found nothing. We cannot rule an interaction out.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Hydroxymethylbutyrate (hmb) safety at a glance

Hydroxymethylbutyr... overall Use caution Generally well tolerated in healthy adults for short-term use, but long-term safety is not well studied.
Pregnancy Avoid Not enough safety data exists, so it is best avoided during pregnancy.
Breastfeeding Avoid There is no reliable safety information, so avoid use while breastfeeding.

Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Cephalexin and Hydroxymethylbutyrate (hmb)? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
What to actually watch for

No Interaction Found — But Data Suggests Hydroxymethylbutyrate (hmb) and Cephalexin May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do.

  • Stomach upset / Stomach pain / Nausea Additional detail

    Hydroxymethylbutyrate (hmb)

    “Orally, abdominal pain, constipation, dyspepsia, flatulence, heartburn, and nausea have been reported rarely in people taking HMB in clinical trials.”

    Hydroxymethylbutyrate (hmb) · Natural Medicines adverse-effect record, reported in constipation.

    3 sources cited
    1. 99245. Berton L, Bano G, Carraro S, et al. Effect of oral beta-hydroxy-beta-methylbutyrate (HMB) supplementation on physical performance in healthy old women over 65 years: An open label randomized controlled trial. PLoS One. 2015;10(11):e0141757. PubMed
    2. 102872. Tritto AC, Bueno S, Rodrigues RMP, Gualano B, Roschel H, Artioli GG. Negligible effects of ß-hydroxy-ß-methylbutyrate free acid and calcium salt on strength and hypertrophic responses to resistance training: a randomized, placebo-controlled study. Int J S PubMed
    3. 108770. Osuka Y, Kojima N, Sasai H, et al. Effects of exercise and/or ß-hydroxy-ß-methylbutyrate supplementation on muscle mass, muscle strength, and physical performance in older women with low muscle mass: a randomized, double-blind, placebo-controlled trial. A PubMed

    Cephalexin

    Listed in the ADVERSE REACTIONS section of the FDA label for Cephalexin. Read the label on DailyMed ›

  • Itching Additional detail

    Hydroxymethylbutyrate (hmb)

    “Orally, itching has been reported in two people taking HMB in clinical trials.”

    Hydroxymethylbutyrate (hmb) · Natural Medicines adverse-effect record, reported in pruritus.

    2 sources cited
    1. 99245. Berton L, Bano G, Carraro S, et al. Effect of oral beta-hydroxy-beta-methylbutyrate (HMB) supplementation on physical performance in healthy old women over 65 years: An open label randomized controlled trial. PLoS One. 2015;10(11):e0141757. PubMed
    2. 102872. Tritto AC, Bueno S, Rodrigues RMP, Gualano B, Roschel H, Artioli GG. Negligible effects of ß-hydroxy-ß-methylbutyrate free acid and calcium salt on strength and hypertrophic responses to resistance training: a randomized, placebo-controlled study. Int J S PubMed

    Cephalexin

    Listed in the ADVERSE REACTIONS section of the FDA label for Cephalexin. Read the label on DailyMed ›

Reported for Hydroxymethylbutyrate (hmb) but not commonly for Cephalexin: raised blood pressure, constipation, bloating or gas and heartburn.

Effects for Cephalexin come from the ADVERSE REACTIONS section of its FDA label; effects for Hydroxymethylbutyrate (hmb) come from the Natural Medicines adverse-effect record, quoted above. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

From our Q&A

Questions About Hydroxymethylbutyrate (hmb) or Cephalexin

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Hydroxymethylbutyrate (hmb) or Cephalexin, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Cephalexin

This page covers Hydroxymethylbutyrate (hmb) only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Cephalexin page lists 61 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Asarabacca (major), Siberian Cocklebur (major), African Wild Potato (moderate) and Aristolochia (moderate).

By severity: 3 major · 47 moderate · 11 minor.

From our pharmacist’s overview on the Cephalexin page

“Cephalexin (Keflex) is one of the most commonly prescribed oral antibiotics, usually for skin and urinary infections, and its supplement list warrants genuine care rather than a quick skim. Three of the 61 ingredients on file rate major.”

Reviewed by 2 · Jul 18, 2026

Open the Cephalexin interaction page

How much people look this up

Where Hydroxymethylbutyrate (hmb) and Cephalexin Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Hydroxymethylbutyrate (hmb)
Steady interest

#1,421 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Cephalexin
Top 5%

#92 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Hydroxymethylbutyrate (hmb) reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Hydroxymethylbutyrate (hmb) and Cephalexin records this page draws on were last updated July 10, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Supplement

About Hydroxymethylbutyrate (hmb)

What is Hydroxymethylbutyrate (hmb)?

  • Building or preserving muscle mass
  • Improving strength with resistance training
  • Reducing muscle breakdown
  • Supporting recovery after exercise
  • Preventing muscle loss in older adults or illness

HMB is a compound made in the body from the amino acid leucine and is sold as a supplement mainly to support muscle. The best evidence suggests it may help slow muscle loss in certain situations, such as during illness, bed rest, or aging, but results in healthy athletes are mixed. It appears generally well tolerated for most adults, but you should check with your pharmacist or doctor before starting it.

Not applicable (HMB is a metabolite of the amino acid leucine) · Capsules, tablets, powder, drink mixes; available as calcium-HMB (CaHMB) and free-acid HMB

An interaction check asks whether these two react with each other — it does not ask whether Hydroxymethylbutyrate (hmb) is a good idea for someone in your situation. Here is what our Hydroxymethylbutyrate (hmb) record says about it on its own.

Hydroxymethylbutyrate (hmb): dosing

There is no single official dose of HMB, and the best amount depends on the goal and the person. Most research has used HMB taken in divided doses across the day, often alongside resistance training or protein intake.The two common forms are calcium-HMB and free-acid HMB, which may be absorbed differently.

From our Hydroxymethylbutyrate (hmb) monograph — the full record covers uses, side effects and every documented interaction.

Read the full Hydroxymethylbutyrate (hmb) monograph & all interactions
Medication

About Cephalexin

What Is Cephalexin Used For?

Brand names: Keflex, Keftab, Cephalex, Lexin

Cephalexin treats bacterial infections caused by susceptible strains of bacteria. It is used for respiratory tract infections, ear infections (otitis media), skin and skin structure infections, bone infections, and genitourinary tract infections — including acute prostatitis.

It works only against bacterial infections — not viruses like colds or flu. Your prescriber should use it only when a bacterial infection is confirmed or strongly suspected, to help prevent antibiotic resistance.

Most-Reported Side Effects for Cephalexin

From FAERS, the FDA’s public side-effect reporting system (0 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Chronic kidney disease 2,157 reports
Renal failure 1,558 reports
Acute kidney injury 1,550 reports
Diarrhea 1,405 reports
Fatigue 1,303 reports
See full Cephalexin drug information
Keep checking

Other Drugs & Hydroxymethylbutyrate (hmb)

Browse every other medication we’ve checked against Hydroxymethylbutyrate (hmb) — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
0Moderate
0Minor
2,829No known interaction
2,829 No interaction
No interaction 2,829 drugs checked — show the list

We also checked Hydroxymethylbutyrate (hmb) against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,829 medications checked with no known interaction — see the full Hydroxymethylbutyrate (hmb) list.

See the full Hydroxymethylbutyrate (hmb) interactions page
See every supplement checked against Cephalexin, ranked by severity
Evidence & sources

Hydroxymethylbutyrate (hmb) References

The 3 references that drive our Hydroxymethylbutyrate (hmb) monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Berton L, Bano G, Carraro S, et al. Effect of oral beta-hydroxy-beta-methylbutyrate (HMB) supplementation on physical performance in healthy old women over 65 years: An open label randomized controlled trial. PLoS One. 2015;10(11):e0141757. PubMed
  2. Tritto AC, Bueno S, Rodrigues RMP, Gualano B, Roschel H, Artioli GG. Negligible effects of ß-hydroxy-ß-methylbutyrate free acid and calcium salt on strength and hypertrophic responses to resistance training: a randomized, placebo-controlled study. Int J S PubMed
  3. Osuka Y, Kojima N, Sasai H, et al. Effects of exercise and/or ß-hydroxy-ß-methylbutyrate supplementation on muscle mass, muscle strength, and physical performance in older women with low muscle mass: a randomized, double-blind, placebo-controlled trial. A PubMed

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Hydroxymethylbutyrate (hmb) and Cephalexin Together: Common Questions

Is it safe to take Hydroxymethylbutyrate (hmb) with Cephalexin?
We do not list a known interaction between Hydroxymethylbutyrate (hmb) and Cephalexin. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
Do Hydroxymethylbutyrate (hmb) and Cephalexin have any of the same side effects?
Yes — our sources link each of them separately to 4 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
Does Cephalexin interact with any supplements?
Yes. Cephalexin has documented interactions with 61 supplements in our database — Hydroxymethylbutyrate (hmb) is not one of them. The Cephalexin interaction page linked on this page lists every one, ranked by severity.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Where next

Keep Exploring

Hydroxymethylbutyrate (hmb) monograph Uses, safety profile, and every drug interaction in one place Cephalexin drug information The full plain-English guide to this medication Cephalexin supplement interactions Every supplement checked against Cephalexin, ranked by severity Supplement interaction checker Check any supplement or product against your medications Browse medications A–Z Every drug we’ve checked against herbs & supplements References The 3 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.