Drug & supplement interaction

Glycomacropeptide + Timolol

Timolol brand names: Blocadren, Timol, Timoptic.

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 Glycomacropeptide and Timolol 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.

Know someone taking this? Share
Facebook Post Reddit Email
On this page
Interaction report

Glycomacropeptide and Timolol

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 Timolol and Glycomacropeptide 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 Glycomacropeptide at all — not against Timolol, 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.

Glycomacropeptide safety at a glance

Glycomacropeptide overall Use caution Generally well tolerated as a food protein, but it is milk-derived and not suitable for those with milk allergy.
Pregnancy Use caution Not enough safety data; use only under medical or dietitian supervision.
Breastfeeding Use caution Not enough safety data; check with your doctor before use.

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

Still wondering about combining Timolol and Glycomacropeptide? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
What to actually watch for

No Interaction Found — But Data Suggests Glycomacropeptide and Timolol 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 / Diarrhea / Nausea Additional detail

    Glycomacropeptide

    “Orally, the most common side effects of glycomacropeptide are abdominal discomfort, bloating, burping, and flatulence. Taking skim milk powder enriched with glycomacropeptide and G600 milk fat extract for 3 months has been associated with diarrhea, flatulence, and nausea. However, rates of these effects were similar in the control group.”

    Glycomacropeptide · Natural Medicines adverse-effect record, reported in diarrhea.

    3 sources cited
    1. 113396. Delsoglio M, Capener R, MacDonald A, et al. Evaluation of a New Glycomacropeptide-Based Protein Substitute in Powdered and Liquid Format in Patients with PKU. Nutrients 2023;15(16):3580. PubMed
    2. 96291. Dalbeth N, Ames R, Gamble GD, et al. Effects of skim milk powder enriched with glycomacropeptide and G600 milk fat extract on frequency of gout flares: a proof-of-concept randomised controlled trial. Ann Rheum Dis. 2012;71(6):929-34. PubMed
    3. 96292. Ney DM, Stroup BM, Clayton MK, et al. Glycomacropeptide for nutritional management of phenylketonuria: a randomized, controlled, crossover trial. Am J Clin Nutr. 2016;104(2):334-45. PubMed

    Timolol

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

Reported for Glycomacropeptide but not commonly for Timolol: bloating or gas.

Effects for Timolol come from the ADVERSE REACTIONS section of its FDA label; effects for Glycomacropeptide 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 Glycomacropeptide or Timolol

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Glycomacropeptide or Timolol, 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 Timolol

This page covers Glycomacropeptide only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Timolol page lists 183 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), American Mistletoe (major), Indian Snakeroot (major) and Tyramine (major).

By severity: 5 major · 151 moderate · 27 minor.

From our pharmacist’s overview on the Timolol page

“The supplement list for timolol (Blocadren, Timoptic) calls for genuine care, starting with its five major-rated entries. Timolol is a beta-blocker that slows the heart and lowers blood pressure, and even the eye-drop form absorbs enough to matter.”

Reviewed by 2 · Jul 18, 2026

Open the Timolol interaction page

How much people look this up

Where Glycomacropeptide and Timolol 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 Glycomacropeptide
Steady interest

#1,134 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Timolol
Top half

#1,075 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 Glycomacropeptide reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Glycomacropeptide and Timolol 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 Glycomacropeptide

What is Glycomacropeptide?

  • Phenylketonuria (PKU) nutrition
  • Protein source low in phenylalanine
  • Gut and digestive health
  • Prebiotic support
  • Appetite and satiety

Glycomacropeptide (GMP) is a milk-derived protein fragment best known as a low-phenylalanine protein source used in medical foods for people with phenylketonuria (PKU). It is also being studied for gut health and appetite, but evidence for most non-PKU uses is still limited. Talk to your doctor or dietitian before using GMP products, especially if you have a metabolic condition.

Peptide derived from milk casein (whey-based) · Medical foods, protein powders, capsules, ready-to-drink formulas

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

Glycomacropeptide: dosing

There is no single standardized dose of glycomacropeptide for general use. The right amount depends on why it is being used. For PKU, the amount is carefully calculated by a metabolic dietitian based on a person's protein needs and phenylalanine limits.For protein powders and other supplements, follow the directions on the product label. Avoid taking more than the label suggests.

From our Glycomacropeptide monograph — the full record covers uses, side effects and every documented interaction.

Read the full Glycomacropeptide monograph & all interactions
Medication

About Timolol

What Is Timolol Used For?

Brand names: Blocadren, Timol, Timoptic

Timolol is available in ophthalmic (eye) forms and as an oral tablet, and each form has its own approved uses. Ophthalmic formulations — including Betimol, Istalol, Timolol GFS, Timolol hemihydrate, Timolol Maleate eye drops, and Timolol Maleate Ophthalmic Gel Forming Solution — are used to lower elevated intraocular pressure (pressure inside the eye) in people with ocular hypertension or open-angle glaucoma.

Timolol Maleate tablets are used orally for three separate conditions: treating high blood pressure (alone or combined with other blood pressure medicines), reducing the risk of death and repeat heart attack in people who have survived a heart attack and are clinically stable, and preventing migraine headaches.

See full Timolol drug information
Keep checking

Other Drugs & Glycomacropeptide

Browse every other medication we’ve checked against Glycomacropeptide — 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 Glycomacropeptide 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 Glycomacropeptide list.

See the full Glycomacropeptide interactions page
See every supplement checked against Timolol, ranked by severity
Evidence & sources

Glycomacropeptide References

The 12 references that drive our Glycomacropeptide 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. van Calcar SC, MacLeod EL, Gleason ST, et al. Improved nutritional management of phenylketonuria by using a diet containing glycomacropeptide compared with amino acids. Am J Clin Nutr 2009;89(4):1068-1077. PubMed
  2. Keogh, J. B. and Clifton, P. The effect of meal replacements high in glycomacropeptide on weight loss and markers of cardiovascular disease risk. Am J Clin Nutr 2008;87(6):1602-1605. DOI
  3. Dalbeth N, Ames R, Gamble GD, et al. Effects of skim milk powder enriched with glycomacropeptide and G600 milk fat extract on frequency of gout flares: a proof-of-concept randomised controlled trial. Ann Rheum Dis. 2012;71(6):929-34. PubMed
  4. Ney DM, Stroup BM, Clayton MK, et al. Glycomacropeptide for nutritional management of phenylketonuria: a randomized, controlled, crossover trial. Am J Clin Nutr. 2016;104(2):334-45. PubMed
  5. Daly A, Evans S, Chahal S, et al. Glycomacropeptide: long-term use and impact on blood phenylalanine, growth and nutritional status in children with PKU. Orphanet J Rare Dis 2019;14(1):44. doi: 10.1186/s13023-019-1011-y. PubMed
  6. Tiele A, Daly A, Hattersley J, et al. Investigation of paediatric PKU breath malodour, comparing glycomacropeptide with phenylalanine free L-amino acid supplements. J Breath Res 2019;14(1):016001. doi: 10.1088/1752-7163/ab4097. PubMed
  7. Larsen ER, Juel A, Jensen E, Hollyer TR, Wegener G. Dietary supplementation with casein glycomacropeptide, leucine and tryptophan reduces plasma amino acid levels in men. Acta Neuropsychiatr 2022;34(2):69-76. PubMed
  8. Delsoglio M, Capener R, MacDonald A, et al. Evaluation of a New 'Mix-In' Style Glycomacropeptide-Based Protein Substitute for Food and Drinks in Patients with Phenylketonuria and Tyrosinemia. Nutrients 2023;15(16):3598. PubMed
  9. Delsoglio M, Capener R, MacDonald A, et al. Evaluation of a New Glycomacropeptide-Based Protein Substitute in Powdered and Liquid Format in Patients with PKU. Nutrients 2023;15(16):3580. PubMed
  10. Daly A, Högler W, Crabtree N, et al. A Three-Year Longitudinal Study Comparing Bone Mass, Density, and Geometry Measured by DXA, pQCT, and Bone Turnover Markers in Children with PKU Taking L-Amino Acid or Glycomacropeptide Protein Substitutes. Nutrients 2 PubMed
  11. Pena MJ, Pinto A, de Almeida MF, et al. Continuous use of glycomacropeptide in the nutritional management of patients with phenylketonuria: a clinical perspective. Orphanet J Rare Dis 2021;16(1):84. PubMed
  12. Daly A, Högler W, Crabtree N, et al. Growth and Body Composition in PKU Children-A Three-Year Prospective Study Comparing the Effects of L-Amino Acid to Glycomacropeptide Protein Substitutes. Nutrients 2021;13(4):1323. 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 Glycomacropeptide and Timolol Together: Common Questions

Is it safe to take Glycomacropeptide with Timolol?
We do not list a known interaction between Glycomacropeptide and Timolol. 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 Glycomacropeptide and Timolol have any of the same side effects?
Yes — our sources link each of them separately to 3 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 Timolol interact with any supplements?
Yes. Timolol has documented interactions with 183 supplements in our database — Glycomacropeptide is not one of them. The Timolol 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

Glycomacropeptide monograph Uses, safety profile, and every drug interaction in one place Timolol drug information The full plain-English guide to this medication Timolol supplement interactions Every supplement checked against Timolol, 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 12 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Timolol and Glycomacropeptide?

Our pharmacists answer your medication & supplement questions — free.

Ask a pharmacist

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.