Drug & supplement interaction

Squill + Doxycyline

Doxycyline brand name: Doxychel.

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

Squill has a moderate interaction with Doxycyline. 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?
Know someone taking this? Share
Facebook Post Reddit Email
On this page
Interaction report

Squill and Doxycyline

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

Moderate

TETRACYCLINE ANTIBIOTICS

Why this applies to Doxycyline

Doxycyline falls under TETRACYCLINE ANTIBIOTICS — the group Squill interacts with.

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 gist for doxycycline and squill. Squill is loaded with cardiac glycosides, the same kind of heart-active compounds found in digoxin. The concern isn't that doxycycline changes your heart directly. Instead, antibiotics like doxycycline can shift the gut bacteria that normally break down some of these glycosides. With less of that breakdown happening, more of squill's potent heart compounds could get absorbed, nudging their levels up.

I'll be honest: this is a theoretical interaction based on how the drugs behave, not on solid studies. But squill itself is risky and hard to dose safely, and even small increases in cardiac glycosides can cause nausea, an irregular or slow heartbeat, or vision changes. Please don't combine them without running it by your pharmacist or doctor first.

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 Doxycyline 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. Doxycyline)
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 Doxycyline

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 Doxycyline, 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 Doxycyline

This page covers Squill only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Doxycyline page lists 149 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Asarabacca (major), Beer (major), Oleander (major), Siberian Cocklebur (major) and St. John's Wort (major).

By severity: 6 major · 132 moderate · 11 minor.

From our pharmacist’s overview on the Doxycyline page

“I read the supplement list for doxycycline (Doxychel) as one to approach with real care, starting with its major-rated entries. Heavy alcohol, including beer and wine, adds to the liver strain this antibiotic can cause, botanicals such as Siberian cocklebur can compound stress on the kidneys, and St.”

Reviewed by 2 · Jul 18, 2026

Open the Doxycyline 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 Doxycyline 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 Doxycyline 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

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

29 days ago today
Medication Doxycyline
Top half

#1,416 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 Doxycycline

What Is Doxycycline Used For?

Brand name: Doxychel

Doxycycline belongs to the tetracycline family of antibiotics. It's prescribed for many types of bacterial infections, including respiratory tract infections, sexually transmitted infections (STIs), tick-borne illnesses like Rocky Mountain spotted fever, and eye infections. It's also used to help prevent malaria and, in some cases, as a helper treatment for severe acne.

In situations where penicillin-type antibiotics can't be used — due to allergy, for example — doxycycline can step in as an alternative. It should only be used for infections that are proven or strongly suspected to be caused by bacteria.

See full Doxycycline 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 Doxycyline, 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 Doxycyline supplement interactions › Every supplement checked against Doxycyline, ranked by severity Doxycycline 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 Doxycyline Together: Common Questions

Can you take Squill with Doxycyline?
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 Doxycyline 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 Doxycyline and Squill?

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.