Drug & supplement interaction

Rehmannia + Hydrochlorothiazide, Methyldopa

Hydrochlorothiazide, Methyldopa brand names: Aldoril 15, Methazide, Aldoril 25, Aldoril D30.

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

Rehmannia has a moderate interaction with Hydrochlorothiazide, Methyldopa. Theoretically, rehmannia might increase the risk of hypotension when taken with antihypertensive drugs.

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

Rehmannia and Hydrochlorothiazide, Methyldopa

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

Moderate

ANTIHYPERTENSIVE DRUGS

Why this applies to Hydrochlorothiazide, Methyldopa

Hydrochlorothiazide, Methyldopa falls under ANTIHYPERTENSIVE DRUGS — the group Rehmannia interacts with.

Theoretically, rehmannia might increase the risk of hypotension when taken with antihypertensive drugs.
Animal research shows that rehmannia may have hypotensive effects. Laboratory research shows that formulations of dried and processed rehmannia root inhibit angiotensin-converting enzyme (ACE).
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: your combo pill pairs hydrochlorothiazide (a water pill) with methyldopa, and both work to bring your blood pressure down. In animal and lab studies, rehmannia appeared to have its own mild blood-pressure-lowering activity, partly by acting a bit like an ACE inhibitor. So the worry is simply additive: rehmannia may nudge your pressure lower on top of what your medicine already does.

If your blood pressure drops too far, you might feel dizzy, lightheaded, tired, or faint, especially standing up. Honestly though, this is theoretical and based only on lab and animal research, not human studies, so don't panic. Just loop in your pharmacist or doctor before adding rehmannia, and keep an eye on your readings.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Chao CH, Hsu JL, Chen MF, et al. Anti-hypertensive effects of Radix Rehmanniae and its active ingredients. Nat Prod Res. 2020;34(11):1547-1552.

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

Rehmannia Also Interacts With Other Medications

Rehmannia has 257 moderate known drug interactions in our database — the Hydrochlorothiazide, Methyldopa one above is one of them. If you take anything else, check it against the full list below.

Moderate 257 No known interaction 2,573 (incl. Hydrochlorothiazide, Methyldopa)
Taking anything else?

Check Another of Your Medications Against Rehmannia

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

Everything else you take

See Every Supplement That Interacts With Hydrochlorothiazide, Methyldopa

This page covers Rehmannia only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Hydrochlorothiazide, Methyldopa page lists 261 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), Asarabacca (major) and Beer (major).

By severity: 13 major · 223 moderate · 25 minor.

From our pharmacist’s overview on the Hydrochlorothiazide, Methyldopa page

“If you take hydrochlorothiazide with methyldopa (Aldoril, Methazide), this list deserves real attention, and the 13 major-rated entries are where to start. Most of the 261 ingredients either push blood pressure lower than intended or add to the diuretic effect, which can drain potassium.”

Reviewed by 2 · Jul 18, 2026

Open the Hydrochlorothiazide, Methyldopa interaction page

One more smart check

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

We hold 861 real supplement products containing Rehmannia, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Rehmannia. Your product may carry other ingredients that interact with Hydrochlorothiazide, Methyldopa too, on top of Rehmannia — 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 Rehmannia and Hydrochlorothiazide, Methyldopa 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 Rehmannia
Top 25%

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

29 days ago today
Medication Hydrochlorothiazide, Methyldopa
Top 10%

#256 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 Rehmannia

What is Rehmannia?

  • Kidney and adrenal support
  • Anemia and blood building (traditional)
  • Inflammatory conditions
  • Allergies
  • Fatigue and aging-related complaints

Rehmannia is a root used for centuries in Traditional Chinese Medicine, often to 'tonify' the kidneys and support energy or blood health. Human evidence for most modern uses is limited, so it should be viewed as unproven rather than reliable. Talk with a pharmacist or doctor before trying it, especially if you are pregnant, breastfeeding, or take other medicines.

Read the full Rehmannia monograph & all interactions
Keep checking

Other Drugs & Rehmannia

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

0Major
257Moderate
0Minor
2,572No known interaction
257 Moderate 2,572 No interaction
Moderate

257 interactions

Showing 60 of 257 moderate interactions — see all 257 on the Rehmannia page.

No interaction 2,572 drugs checked — show the list

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

Showing the 60 most looked-up of 2,572 medications checked with no known interaction — see the full Rehmannia list.

See the full Rehmannia interactions page
See every supplement checked against Hydrochlorothiazide, Methyldopa, 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
Rehmannia monograph › Uses, safety, and every drug interaction in one place Hydrochlorothiazide, Methyldopa supplement interactions › Every supplement checked against Hydrochlorothiazide, Methyldopa, 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 Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Rehmannia and Hydrochlorothiazide, Methyldopa Together: Common Questions

Can you take Rehmannia with Hydrochlorothiazide, Methyldopa?
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 Rehmannia and Hydrochlorothiazide, Methyldopa 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 Hydrochlorothiazide, Methyldopa and Rehmannia?

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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.