Drug & supplement interaction

Grapefruit + Insulin (rDNA)

Insulin (rDNA) brand names: Humalog, Humalog Mix 75/25, Humulin R, Humulin N, Humulin L, and others.

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 Grapefruit and Insulin (rDNA) 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 label for Insulin (rDNA) states a food rule worth keeping to, and 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

Grapefruit and Insulin (rDNA)

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 Insulin (rDNA) and Grapefruit 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.

Grapefruit safety at a glance

Grapefruit overall Use caution The fruit is safe to eat for most people, but it interacts with many medicines.
Pregnancy Use caution Eating grapefruit as food is generally fine, but concentrated supplements should be avoided unless approved by your doctor.
Breastfeeding Use caution Grapefruit as food is generally acceptable, but the safety of concentrated extracts is not well studied.

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

Still wondering about combining Insulin (rDNA) and Grapefruit? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Insulin (rDNA)

Interactions in our licensed database are recorded against drug classes, not just single drug names. Insulin (rDNA) is filed under 2 classifications — including antidiabetes drugs. Grapefruit has documented interactions with 62 drug classes — the most serious being amiodarone (cordarone) (major), artemether (artenam, paluther) (major) and benzodiazepines (major) — and none of Insulin (rDNA)’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

Grapefruit Does Interact With Other Medications

Grapefruit has 776 major, 151 moderate, 63 minor known drug interactions in our database — Insulin (rDNA) isn’t one of them. If you take anything else, check it against the full list below.

Major 776 Moderate 151 Minor 63 No known interaction 1,840 (incl. Insulin (rDNA))
Taking anything else?

Check Another of Your Medications Against Grapefruit

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

What to actually watch for

No Interaction Found — But Data Suggests Grapefruit and Insulin (rDNA) 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. One of them is worth acting on rather than waiting out — marked below.

  • An allergic reaction Worth acting on Additional detail

    Grapefruit

    “Orally, grapefruit and grapefruit juice are generally well tolerated.

    Serious Adverse Effects (Rare):

    Orally: Allergic reactions in sensitive individuals have been reported. When large quantities are consumed, arrhythmias, mineralocorticoid excess, QT prolongation, and pseudohyperaldosteronism have been reported. There is also some concern for increased breast cancer risk with grapefruit consumption.”

    Grapefruit · Natural Medicines adverse-effect record, reported in arrhythmia.

    Insulin (rDNA)

    Listed in the ADVERSE REACTIONS section of the FDA label for Insulin (rDNA). Read the label on DailyMed ›

  • Itching Additional detail

    Grapefruit

    “Orally, grapefruit can cause allergic sensitization characterized by eosinophilic gastroenteritis, urticaria, and generalized pruritus.”

    Grapefruit · Natural Medicines adverse-effect record, reported in pruritus.

    2 sources cited
    1. 53351. Kumar, A., Teuber, S. S., Naguwa, S., Prindiville, T., and Gershwin, M. E. Eosinophilic gastroenteritis and citrus-induced urticaria. Clin Rev Allergy Immunol 2006;30(1):61-70. PubMed
    2. 53360. Ferdman, R. M., Ong, P. Y., and Church, J. A. Pectin anaphylaxis and possible association with cashew allergy. Ann.Allergy Asthma Immunol. 2006;97(6):759-760. PubMed

    Insulin (rDNA)

    Listed in the ADVERSE REACTIONS section of the FDA label for Insulin (rDNA). Read the label on DailyMed ›

Reported for Grapefruit but not commonly for Insulin (rDNA): an irregular heartbeat, kidney stones and hives.

Effects for Insulin (rDNA) come from the ADVERSE REACTIONS section of its FDA label; effects for Grapefruit 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.

How to take them

Some Insulin (rDNA) Products Have a Food Rule — Grapefruit Should Not Break It

At least one FDA label for a product containing Insulin (rDNA) says to take it with food. If you take Grapefruit on an empty stomach out of habit, keep them separate — and take Insulin (rDNA) with a meal where the label says to.

This may not be true of your version. Food instructions belong to the product, not the ingredient: two Insulin (rDNA) products can carry different directions, and extended-release forms often differ from immediate-release ones. The label we read is quoted below — check the directions on your own box or bottle, or ask your pharmacist, for how to take the exact product you were given.

( 2.1 , 2.2 , 2.3 , 2.4 ) Subcutaneous injection ( 2.2 ): Administer HUMALOG ® U-100 or U-200 by subcutaneous injection into the abdominal wall, thigh, upper arm, or buttocks within 15 minutes before a meal or immediately after a meal.

From the Dosage and Administration section of the FDA label we read for Insulin (rDNA) — where that label names a specific product, the instruction is that product's. Read the label on DailyMed ›

A food rule is not an interaction — it is about how much of the medicine you absorb. The directions that came with your own product, and your pharmacist, outrank anything on this page.

From our Q&A

Questions About Grapefruit or Insulin (rDNA)

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Grapefruit or Insulin (rDNA), 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 Insulin (rDNA)

This page covers Grapefruit only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Insulin (rDNA) page lists 242 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Chelation Therapy Products (major), Siberian Cocklebur (major), Acai (moderate), African Wild Potato (moderate) and Agaricus Mushroom (moderate).

By severity: 2 major · 211 moderate · 29 minor.

From our pharmacist’s overview on the Insulin (rDNA) page

“A weed called Siberian cocklebur has caused severe low blood sugar in humans and is the one ingredient to avoid outright while using insulin (rDNA) products like Humalog or Humulin. This list deserves real respect.”

Reviewed by 2 · Jul 18, 2026

Open the Insulin (rDNA) interaction page

One more smart check

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

We hold 1,144 real supplement products containing Grapefruit, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Grapefruit. Even though Grapefruit itself has no known interaction with Insulin (rDNA), 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 Grapefruit and Insulin (rDNA) 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 Grapefruit
Top 10%

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

29 days ago today
Medication Insulin (rDNA)
Top half

#877 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 Grapefruit reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Grapefruit and Insulin (rDNA) 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 Grapefruit

What is Grapefruit?

Grapefruit
  • Source of vitamin C
  • Digestive complaints
  • Antimicrobial (seed extract)
  • Weight management
  • Skin and cosmetic uses

Grapefruit is a nutritious citrus fruit rich in vitamin C and other nutrients, and it is generally safe to eat. However, grapefruit is famous for serious interactions with many prescription medicines, so anyone taking medication should check with a pharmacist or doctor before consuming it regularly.

Citrus paradisi · Rutaceae · Fruit, juice, peel, and seed extract · Fresh fruit, juice, seed extract (capsules or liquid), essential oil

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

Grapefruit: dosing

There is no official standardized dose for grapefruit as a supplement. Grapefruit is most often simply eaten as a fruit or consumed as juice as part of a normal diet.For grapefruit seed extract and other concentrated products, there is no well-established effective or safe dose.

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

Read the full Grapefruit monograph & all interactions
Medication

About Insulin Lispro Injection

What Is Insulin Lispro Injection Used For?

Brand names: Humalog, Humalog Mix 75/25, Humulin R, Humulin N, Humulin L, Humulin 50/50, Humulin 70/30, Humulin U, NovoLog, Velosulin, Novolog Mix 70/30, Actrapid, Humulin S, Insuman Rapid

Insulin lispro injection is used to improve glycemic control (blood sugar management) in people with diabetes mellitus. It is a rapid-acting insulin analog approved for use in both type 1 and type 2 diabetes.

Admelog is specifically indicated to improve glycemic control in patients with diabetes mellitus. Humalog Mix75/25 is indicated to improve glycemic control in adults with diabetes mellitus; it is a fixed-ratio mixture of insulin lispro and insulin lispro protamine, and its fixed proportions do not allow for separate adjustment of basal (background) and prandial (mealtime) doses.

See full Insulin Lispro Injection drug information
Keep checking

Other Drugs & Grapefruit

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

776Major
151Moderate
63Minor
1,839No known interaction
776 Major 151 Moderate 63 Minor 1,839 No interaction
Major

776 interactions

Showing 60 of 776 major interactions — see all 776 on the Grapefruit page.

Moderate

151 interactions

Showing 60 of 151 moderate interactions — see all 151 on the Grapefruit page.

Minor

63 interactions

Showing 60 of 63 minor interactions — see all 63 on the Grapefruit page.

No interaction 1,839 drugs checked — show the list

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

Showing the 60 most looked-up of 1,839 medications checked with no known interaction — see the full Grapefruit list.

See the full Grapefruit interactions page
See every supplement checked against Insulin (rDNA), ranked by severity
Evidence & sources

Grapefruit References

The 157 references that drive our Grapefruit 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. Penzak SR, Gubbins PO, Gurley BJ, et al. Grapefruit juice decreases the systemic availability of itraconazole capsules in healthy volunteers. Ther Drug Monit 1999;21:304-9. PubMed
  2. Ioannides-Demos LL, Christophidis N, et al. Dosing implications of a clinical interaction between grapefruit juice and cyclosporine and metabolite concentrations in patients with autoimmune diseases. J Rheumatol 1997;24:49-54.
  3. Josefsson M, Zackrisson AL, Ahlner J. Effect of grapefruit juice on the pharmacokinetics of amlodipine in healthy volunteers. Eur J Clin Pharmacol 1996;51:189-93. PubMed
  4. Garg SK, Kumar N, Bhargava VK, Prabhakar SK. Effect of grapefruit juice on carbamazepine bioavailability in patients with epilepsy. Clin Pharmacol Ther 1998;64:286-8. PubMed
  5. Weber A, Jager R, Borner A, et al. Can grapefruit juice influence ethinylestradiol bioavailability? Contraception 1996;53:41-7.
  6. Schubert W, Cullberg G, Edgar B, Hedner T. Inhibition of 17 beta-estradiol metabolism by grapefruit juice in ovariectomized women. Maturitas 1994;20:155-63.
  7. Kantola T, Kivisto KT, Neuvonen PJ, et al. Grapefruit juice greatly increases serum concentrations of lovastatin and lovastatin acid. Clin Pharmacol Ther 1998 63:397-402. PubMed
  8. Bailey DG, Spence JD, Munoz C, Arnold JM. Interaction of citrus juices with felodipine and nifedipine. Lancet 1991;337:268-9. PubMed
  9. Bailey DG, Arnold JM, Strong HA, et al. Effect of grapefruit juice and naringin on nisoldipine pharmacokinetics. Clin Pharmacol Ther 1993;54:589-94. PubMed
  10. Rau SE, Bend JR, Arnold MO, et al. Grapefruit juice-terfenadine single-dose interaction: magnitude, mechanism, and relevance. Clin Pharmacol Ther 1997 61:401-9. PubMed
  11. Offman EM, Freeman DJ, Dresser GK, et al. Cisapride interaction with grapefruit juice and red wine. Clin Pharmacol Ther 2000;67:110 (abstract PI-83).
  12. Bailey DG, Dresser GK, Kreeft JH, et al. Grapefruit juice-felodipine interaction: Effect of segments and an extract from unprocessed fruit. Clin Pharmacol Ther 2000;67:107 (abstract PI-71).
  13. Soldner A, Christians U, Susanto M, et al. Grapefruit juice activates P-glycoprotein-mediated drug transport. Pharm Res 1999;16:478-85. PubMed
  14. Zaidenstein R, Avni B, Dishi V, et al. Effect of grapefruit juice on the pharmacokinetics of losartan in healthy volunteers. Clin Pharmacol Ther 1998;65:(abstract PI-60). DOI
  15. Dresser GK, Bailey DG, Carruthers SG. Grapefruit juice-felodipine interaction in healthy seniors. Clin Pharmacol Ther 1998;65:(abstract PIII-63).

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 Grapefruit and Insulin (rDNA) Together: Common Questions

Is it safe to take Grapefruit with Insulin (rDNA)?
We do not list a known interaction between Grapefruit and Insulin (rDNA). 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 Grapefruit and Insulin (rDNA) 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.
Should I take Grapefruit and Insulin (rDNA) at the same time of day?
At least one FDA label for a product containing Insulin (rDNA) says to take it with food. If you take Grapefruit on an empty stomach out of habit, keep them separate and take Insulin (rDNA) with a meal where the label says to. Food instructions belong to the product rather than the ingredient — two Insulin (rDNA) products can differ — so check the directions on your own box. This is about absorption, not an interaction.
How was the Grapefruit and Insulin (rDNA) combination checked?
Interactions in our licensed database are recorded against drug classes. Insulin (rDNA) is filed under 2 classifications, and Grapefruit has documented interactions with 62 drug classes — none of Insulin (rDNA)'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 Grapefruit interact with any other medications?
Yes. Grapefruit has 990 documented drug interactions in our database — Insulin (rDNA) 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 Insulin (rDNA) interact with any supplements?
Yes. Insulin (rDNA) has documented interactions with 242 supplements in our database — Grapefruit is not one of them. The Insulin (rDNA) 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

Grapefruit monograph Uses, safety profile, and every drug interaction in one place Insulin Lispro Injection drug information The full plain-English guide to this medication Insulin (rDNA) supplement interactions Every supplement checked against Insulin (rDNA), 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 157 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Insulin (rDNA) and Grapefruit?

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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.