Drug & supplement interaction

Squill + Tetracycline

Tetracycline brand names: Sumycin, Sumycin 250, Tetrex BID, Achromycin V, Robitet, and others.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Squill has a moderate interaction with Tetracycline. Tetracycline antibiotics appear to increase the gastrointestinal absorption of oral digoxin.

Read the full interaction report
SeverityModerate
LikelihoodPossible
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Squill and Tetracycline

Here is the interaction we found between these two, with the evidence behind it.

Moderate

TETRACYCLINE ANTIBIOTICS

Tetracycline antibiotics appear to increase the gastrointestinal absorption of oral digoxin. Theoretically, concomitant use of tetracycline antibiotics might increase the absorption of the cardiac glycosides found in squill.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the connection with squill and tetracycline. Squill contains its own heart-acting compounds called cardiac glycosides, which behave a lot like the drug digoxin. There's a thought that tetracycline antibiotics may change the gut bacteria that normally break down some of these glycosides, leaving more of them to be absorbed. In theory, that could mean more squill ends up in your system than expected.

If that happened, you'd worry about too much heart-glycoside effect: nausea, loss of appetite, blurred or yellow-tinged vision, and irregular or slow heartbeats. I'll be honest, this is a theoretical concern based on how these drugs work, not strong human studies. Still, squill itself can be quite toxic, so please loop in your pharmacist or doctor before combining them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Ellenhorn MJ, et al. Ellenhorn's Medical Toxicology: Diagnoses and Treatment of Human Poisoning. 2nd ed. Baltimore, MD: Williams & Wilkins, 1997.

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Squill Also Interacts With Other Medications

Squill has 1 major, 154 moderate known drug interactions in our database — the Tetracycline one above is one of them. If you take anything else, check it against the full list below.

Major 1 Moderate 154 No known interaction 2,675 (incl. Tetracycline)
Taking anything else?

Check Another of Your Medications Against Squill

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

From our Q&A

Questions About Squill or Tetracycline

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

This page covers Squill only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Tetracycline page lists 164 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Asarabacca (major), Beer (major), Oleander (major) and Siberian Cocklebur (major).

By severity: 7 major · 136 moderate · 21 minor.

Open the Tetracycline interaction page

One more smart check

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

We hold 2 real supplement products containing Squill, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Squill. Your product may carry other ingredients that interact with Tetracycline too, on top of Squill — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Squill and Tetracycline 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 Squill
Top half

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

29 days ago today
Medication Tetracycline
Steady interest

#1,574 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.

Supplement

About Squill

What is Squill?

Squill
  • Cough and chest congestion
  • Fluid retention (diuretic)
  • Heart conditions (traditional 'cardiac tonic')
  • Hair loss (topical use)
  • Rodenticide (red squill, non-medicinal)

Squill is a bulb plant that contains potent cardiac glycosides, which can affect the heart much like the drug digoxin. While it has a long history of use as a cough remedy and heart tonic, it can be dangerously toxic and there is little solid evidence for its modern use, so we do not recommend taking it without close medical supervision.

Read the full Squill monograph & all interactions
Medication

About Tetracycline

What Is Tetracycline Used For?

Brand names: Sumycin, Sumycin 250, Tetrex BID, Achromycin V, Robitet, Sumycin 500, Tetra, Nor-Tet, Tetracyn, Tetrex, Achromycin, Terramycin IM

Oral tetracycline (tablets and capsules) treats infections caused by susceptible bacteria, including upper and lower respiratory tract infections, skin and soft tissue infections, and sexually transmitted infections such as those caused by Chlamydia trachomatis. It is also used for tick- and flea-borne illnesses like Rocky Mountain spotted fever and typhus, as well as cholera, brucellosis, tularemia, plague, and several other serious bacterial infections.

Topical tetracycline products — including ointments, sprays, and solutions sold under brand names such as Tetracyte, Vitastem, Viabecline, Honestly Battleborn, and ViaDerma Care — are over-the-counter first-aid products used to help prevent skin infection in minor cuts, scrapes, and burns. These topical products are not used for systemic (whole-body) infections.

See full Tetracycline drug information
Keep checking

Other Drugs & Squill

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

1Major
154Moderate
0Minor
2,674No known interaction
1 Major 154 Moderate 2,674 No interaction
Major

1 interaction

Moderate

154 interactions

Showing 60 of 154 moderate interactions — see all 154 on the Squill page.

No interaction 2,674 drugs checked — show the list

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

Showing the 60 most looked-up of 2,674 medications checked with no known interaction — see the full Squill list.

See the full Squill interactions page
See every supplement checked against Tetracycline, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Squill monograph › Uses, safety, and every drug interaction in one place Tetracycline supplement interactions › Every supplement checked against Tetracycline, ranked by severity Tetracycline drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Squill and Tetracycline Together: Common Questions

Can you take Squill with Tetracycline?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Squill and Tetracycline interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

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

Still Have a Question About Tetracycline and Squill?

Our pharmacists answer your medication & supplement questions — free.

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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.