Drug & supplement interaction

Hydroxymethylbutyrate (hmb) + Fosfomycin

Fosfomycin brand name: Monurol.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 13, 2026
The bottom line No known interaction

We found no known interaction between Hydroxymethylbutyrate (hmb) and Fosfomycin 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 Fosfomycin

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 Fosfomycin 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 Fosfomycin, 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 Fosfomycin and Hydroxymethylbutyrate (hmb)? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
What to actually watch for

No Interaction Found — But Data Suggests Hydroxymethylbutyrate (hmb) and Fosfomycin 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 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

    Fosfomycin

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

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

Effects for Fosfomycin 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.

Everything else you take

See Every Supplement That Interacts With Fosfomycin

This page covers Hydroxymethylbutyrate (hmb) only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Fosfomycin page lists 44 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Bacillus Coagulans (moderate), Bacillus Subtilis (moderate), Bifidobacterium Animalis Subsp. Lactis (moderate) and Bifidobacterium Bifidum (moderate).

By severity: 1 major · 33 moderate · 10 minor.

From our pharmacist’s overview on the Fosfomycin page

“Fosfomycin (Monurol) is often given as a single sachet to knock out a bladder infection, so you get one chance to absorb the full dose, and that is exactly where this list deserves real care. The clearest hazard is activated charcoal, which binds medicines in the gut and can cut how much fosfomycin your body actually takes in.”

Reviewed by 2 · Jul 18, 2026

Open the Fosfomycin interaction page

How much people look this up

Where Hydroxymethylbutyrate (hmb) and Fosfomycin 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

#1,246 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Fosfomycin
Steady interest

#2,466 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 13, 2026. The Hydroxymethylbutyrate (hmb) and Fosfomycin 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 Fosfomycin

What Is Fosfomycin Used For?

Brand name: Monurol

Fosfomycin is an antibiotic used to treat urinary tract infections (UTIs) caused by specific bacteria. The right form depends on how serious the infection is.

Oral forms (Fosfomycin Tromethamine and Monurol) are approved only for uncomplicated UTIs — also called acute cystitis — in women 18 and older, caused by E. coli or Enterococcus faecalis. They are not for kidney infections or abscesses around the kidney. Contepo (intravenous) is approved for adults 18 and older with complicated UTIs, including acute pyelonephritis (kidney infection), caused by susceptible E. coli or Klebsiella pneumoniae.

See full Fosfomycin 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 Fosfomycin, 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 Fosfomycin Together: Common Questions

Is it safe to take Hydroxymethylbutyrate (hmb) with Fosfomycin?
We do not list a known interaction between Hydroxymethylbutyrate (hmb) and Fosfomycin. 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 Fosfomycin have any of the same side effects?
Yes — our sources link each of them separately to 2 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 Fosfomycin interact with any supplements?
Yes. Fosfomycin has documented interactions with 44 supplements in our database — Hydroxymethylbutyrate (hmb) is not one of them. The Fosfomycin 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 Fosfomycin drug information The full plain-English guide to this medication Fosfomycin supplement interactions Every supplement checked against Fosfomycin, 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.