Drug & supplement interaction

Wheatgrass + Phenylephrine

Phenylephrine brand names: Gilchew, AH Chew D, Gilchew IR, Sudafed PE, Biorphen.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 27, 2026
The bottom line No known interaction

We found no known interaction between Wheatgrass and Phenylephrine 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

Wheatgrass and Phenylephrine

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 Phenylephrine and Wheatgrass 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.

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.

Wheatgrass safety at a glance

Wheatgrass overall Use caution Generally well tolerated as a food, but quality and contamination concerns mean caution is wise.
Pregnancy Avoid Safety is not established, and raw products may carry contamination risk, so avoid unless cleared by your doctor.
Breastfeeding Avoid There is not enough safety information, so avoid unless your doctor approves.

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

Still wondering about combining Phenylephrine and Wheatgrass? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Phenylephrine

Interactions in our licensed database are recorded against drug classes, not just single drug names. Phenylephrine is filed under 5 classifications — including alpha-adrenergic agonists, stimulant drugs, serotonergic drugs. Wheatgrass has documented interactions with 2 drug classes — the most serious being antidiabetes drugs (moderate) and cytochrome p450 1a2 (cyp1a2) substrates (moderate) — and none of Phenylephrine’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Wheatgrass Does Interact With Other Medications

Wheatgrass has 272 moderate known drug interactions in our database — Phenylephrine isn’t one of them. If you take anything else, check it against the full list below.

Moderate 272 No known interaction 2,558 (incl. Phenylephrine)
Taking anything else?

Check Another of Your Medications Against Wheatgrass

Covers the 2,830 medications we’ve checked against Wheatgrass. Pick one to open its full report.

What to actually watch for

No Interaction Found — But Data Suggests Wheatgrass and Phenylephrine May Share a Side Effect

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.

  • Nausea reported in 7.6% of FDA reports for Phenylephrine Additional detail

    Wheatgrass

    “Orally, wheatgrass may cause nausea, anorexia, and constipation.”

    Wheatgrass · Natural Medicines adverse-effect record, reported in anorexia.

    1 source cited
    1. 11165. Ben-Arye E, Golden E, Wengrower D, et al. Wheat grass juice in the treatment of active distal ulcerative colitis a randomized double-blind placebo-controlled trial. Scand J Gastroenterol 2002;4:444-9.. PubMed

    Phenylephrine

    Listed in the ADVERSE REACTIONS section of the FDA label for Phenylephrine, and in voluntary FDA adverse-event reports. Read the label on DailyMed ›

Reported for Wheatgrass but not commonly for Phenylephrine: an allergic reaction, constipation and reduced appetite.

Effects for Phenylephrine come from the ADVERSE REACTIONS section of its FDA label; effects for Wheatgrass come from the Natural Medicines adverse-effect record, quoted above. Where a percentage is shown, it is the share of 221,388 voluntary FDA FAERS reports for Phenylephrine that mention that effect — a reporting proportion, not an incidence rate and not evidence the drug caused it. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Overlapping uses

What Phenylephrine Is Prescribed For, and What Wheatgrass Has Been Studied For

These two come up together because they touch the same health topic — not because they do the same job. Phenylephrine is a prescription medicine with approved uses on its FDA label. Wheatgrass is a supplement: what follows is what researchers have looked at it for, and how strong that evidence is.

Phenylephrine is prescribed for: Phenylephrine is used in several different products, and each one has its own use. Injection (IV): raises blood pressure in adults with clinically important hypotension (low blood pressure) caused mainly by widened blood vessels. Some injections are labeled for anesthesia only. Others are labeled for anesthesia and septic shock.

Read the rest of what Phenylephrine is prescribed for

Eye drops: Phenylephrine Hydrochloride Ophthalmic Solution is used to dilate the pupil. Nasal products: temporarily relieve nasal and sinus congestion from the common cold, hay fever or other upper respiratory allergies. Rectal suppositories: relieve itching, burning and discomfort from hemorrhoids and temporarily shrink hemorrhoidal tissue.

Wheatgrass has been studied for:

  • Common cold studied, not established Wheatgrass has been studied for this. Natural Medicines rates the evidence: Insufficient Reliable Evidence To Rate Read what the research shows

    Wheatgrass for common cold

    Although there has been interest in using oral wheatgrass for common cold, there is insufficient reliable information about the clinical effects of wheatgrass for this purpose.

Effectiveness ratings and the research summaries above are the verbatim record from the Natural Medicines database, which grades evidence from “Effective” down to “Insufficient Reliable Evidence To Rate”. A rating below the top of that scale means researchers have looked at it — not that it works, and never that it can stand in for a prescribed medicine. Do not stop or replace Phenylephrine on your own; if you are taking Wheatgrass for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

From our Q&A

Questions About Wheatgrass or Phenylephrine

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

This page covers Wheatgrass only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Phenylephrine page lists 81 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Ephedra (major), Lithium (major), Peyote (major) and Rauvolfia Vomitoria (major).

By severity: 6 major · 60 moderate · 15 minor.

From our pharmacist’s overview on the Phenylephrine page

“If you take phenylephrine (Sudafed PE, Biorphen) for congestion, treat this list as one that needs real attention, since six of its 81 entries carry a major rating. Phenylephrine tightens blood vessels to clear your nose, and more than half of the interactions here come from stimulant ingredients, ephedra above all, that can push blood…”

Reviewed by 2 · Jul 18, 2026

Open the Phenylephrine interaction page

One more smart check

Taking Wheatgrass as Part of a Dietary Supplement Product? Check It for Interactions

We hold 104 real supplement products containing Wheatgrass, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Wheatgrass. Even though Wheatgrass itself has no known interaction with Phenylephrine, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Wheatgrass and Phenylephrine 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 Wheatgrass
Top half

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

29 days ago today
Medication Phenylephrine
Top half

#799 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 Wheatgrass reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 27, 2026. The Wheatgrass and Phenylephrine 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 Wheatgrass

What is Wheatgrass?

Wheatgrass
  • General nutrition support
  • Digestive health
  • Antioxidant support
  • Energy and wellness
  • Arthritis symptoms
  • Detox or cleansing routines

Wheatgrass is the young grass of the wheat plant, taken as a juice or powder, and is mainly used as a concentrated source of vitamins and plant nutrients. Solid scientific evidence for most health claims is limited, and it is best viewed as a nutritional add-on rather than a treatment. It is generally well tolerated, but people with celiac disease, wheat allergy, or who are pregnant should be cautious and check with a healthcare provider.

Triticum aestivum · Poaceae · Young grass (leaves/shoots) of the wheat plant · Fresh juice, powder, tablets, capsules, and added to smoothies or health drinks

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

Wheatgrass: dosing

There is no official or standardized dose for wheatgrass. Amounts vary widely between fresh juice, powder, and tablets, so the right amount depends on the specific product.The safest approach is to follow the directions on the product label and start with a small amount to see how your body responds.

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

Read the full Wheatgrass monograph & all interactions
Medication

About Phenylephrine

What Is Phenylephrine Used For?

Brand names: Gilchew, AH Chew D, Gilchew IR, Sudafed PE, Biorphen

Phenylephrine is used in several different products, and each one has its own use.

Injection (IV): raises blood pressure in adults with clinically important hypotension (low blood pressure) caused mainly by widened blood vessels. Some injections are labeled for anesthesia only. Others are labeled for anesthesia and septic shock.

Eye drops: Phenylephrine Hydrochloride Ophthalmic Solution is used to dilate the pupil.

Nasal products: temporarily relieve nasal and sinus congestion from the common cold, hay fever or other upper respiratory allergies.

Rectal suppositories: relieve itching, burning and discomfort from hemorrhoids and temporarily shrink hemorrhoidal tissue.

Most-Reported Side Effects for Phenylephrine

From FAERS, the FDA’s public side-effect reporting system (221,388 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Fatigue 20,609 reports
Headache 17,301 reports
Nausea 16,925 reports
Diarrhea 14,221 reports
Dyspnea 13,719 reports
See full Phenylephrine drug information
Keep checking

Other Drugs & Wheatgrass

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

0Major
272Moderate
0Minor
2,557No known interaction
272 Moderate 2,557 No interaction
Moderate

272 interactions

Showing 60 of 272 moderate interactions — see all 272 on the Wheatgrass page.

No interaction 2,557 drugs checked — show the list

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

Showing the 60 most looked-up of 2,557 medications checked with no known interaction — see the full Wheatgrass list.

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

Wheatgrass References

The 5 references that drive our Wheatgrass 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. Ben-Arye E, Golden E, Wengrower D, et al. Wheat grass juice in the treatment of active distal ulcerative colitis a randomized double-blind placebo-controlled trial. Scand J Gastroenterol 2002;4:444-9.. PubMed
  2. Mohan Y, Jesuthankaraj GN1, Ramasamy Thangavelu N. Antidiabetic and antioxidant properties of Triticum aestivum in streptozotocin-induced diabetic rats. Adv Pharmacol Sci 2013;2013:716073.
  3. Shakya G, Randhi PK, Pajaniradje S, Mohankumar K, Rajagopalan R. Hypoglycaemic role of wheatgrass and its effect on carbohydrate metabolic enzymes in type II diabetic rats. Toxicol Ind Health 2016;32(6):1026-32. PubMed
  4. Food and Drug Administration. Food Allergen Labeling and Consumer Protection Act of 2004 (FALCPA); Public Law 108-282, Title II. Accessed on May 19, 2021. Available at: https://www.fda.gov/food/food-allergensgluten-free-guidance-documents-regulatory-infor
  5. Haron MH, Dale O, Martin K, et al. Evaluation of the Herb-Drug Interaction Potential of Commonly Used Botanicals on the US Market with Regard to PXR- and AhR-Mediated Influences on CYP3A4 and CYP1A2. J Diet Suppl 2022. 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 Wheatgrass and Phenylephrine Together: Common Questions

Is it safe to take Wheatgrass with Phenylephrine?
We do not list a known interaction between Wheatgrass and Phenylephrine. 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 Wheatgrass and Phenylephrine have any of the same side effects?
Yes — our sources link each of them separately to one 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.
Are Wheatgrass and Phenylephrine used for the same thing?
They overlap in purpose, which usually means the real question is whether you need both rather than whether they are safe together. This page lists the shared uses and how strong the evidence is for Wheatgrass in each. That is a conversation for your prescriber, especially if Phenylephrine is being adjusted to a target.
How was the Wheatgrass and Phenylephrine combination checked?
Interactions in our licensed database are recorded against drug classes. Phenylephrine is filed under 5 classifications, and Wheatgrass has documented interactions with 2 drug classes — none of Phenylephrine's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Wheatgrass interact with any other medications?
Yes. Wheatgrass has 272 documented drug interactions in our database — Phenylephrine is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Phenylephrine interact with any supplements?
Yes. Phenylephrine has documented interactions with 81 supplements in our database — Wheatgrass is not one of them. The Phenylephrine 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

Wheatgrass monograph Uses, safety profile, and every drug interaction in one place Phenylephrine drug information The full plain-English guide to this medication Phenylephrine supplement interactions Every supplement checked against Phenylephrine, 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 5 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Phenylephrine and Wheatgrass?

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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.