Liothyronine and Bugleweed: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Liothyronine
Bugleweed
No brand names on record
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Reduced effectiveness of thyroid hormones
Interaction Deep Dive
Lycopus europaeus and Lycopus virginicus (bugleweed) have antithyroid activity and should not be taken with drugs that are intended to alter thyroid function41. Some practitioners of natural medicine have used bugleweed to decrease the required dose of these drugs but expert supervision is required 3.
Why it happens (mechanism)
Bugleweed may decreased T3 levels, possibly the result of peripheral T4 deiodination; bugleweed may change the conformation of TSH, and inhibit cAMP
Literature reports
2 reports — tap to read
a) Oral administration of an ethanol extract of Lycopus europaeus 1000 milligrams/kilogram (mg/kg) resulted in significant reductions (p less than 0.05) in T3 levels beginning at 6 hours and lasting for more than 24 hours compared to controls. T4 levels were significantly decreased compared to controls only after 24 hours. A reduction in thyroid-stimulating hormone (TSH) occurred after 24 hours compared to controls in a controlled study using male Wistar rats. Significant increases in TSH compared to controls were reported at 9 and 12 hours (p values not reported). Oral administration of 200 mg/kg resulted in increases in TSH to 129+/-25 nanogram/milliliter (ng/mL) compared to 26+/-10 ng/mL in control animals. Intraperitoneal (IP) injection of Lycopus europaeus 50 milligrams resulted in significant decreases in T3 (p less than 0.05) and TSH levels at 3 hours (p less than 0.01). At 6 hours the effect was less although TSH remained significantly reduced compared to controls (p less than 0.05). At 9 hours T3, T4 (p less than 0.05 compared to controls), and TSH levels were all increased compared to controls. T4 levels were not significantly different compared to controls at 3 and 6 hours. Male Wistar rats received ethanol preparations of Lycopus europaeus orally by gavage or by IP injections. Rats were sacrificed and thyroid and pituitary glands were examined 3 to 24 hours after treatment. Rats were also sacrificed at 10, 30, 60, and 180 minutes after treatment for evaluation of absorption and metabolism of plant constituents 2.
b) At least 14 uncontrolled clinical trials or case series have been reported in the German medical literature supporting the efficacy of various extracts of Lycopus europaeus or Lycopus virginicus (bugleweed), sometimes with Leonurus cardiaca (motherwort) herb added, in relieving symptoms of hyperthyroidism 3.
Common questions
Can I take Liothyronine and Bugleweed together?
Reduced effectiveness of thyroid hormones Always confirm with your pharmacist or prescriber before making any change.
How serious is the Liothyronine and Bugleweed interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Liothyronine or Bugleweed need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there anything you'd monitor while I'm on both?
References (4)
- Sourgens H, Winterhoff H, Gumbinger HG, et al: Antihormonal effects of plant extracts on hypophyseal hormones in the rat. Acta Endocrinol 1980; 234(suppl):49. DOI
- Winterhoff H, Gumbinger HG, & Sourgens H: On the antigonadotropic activity of Lithospermum and Lycopus species and some of their phenolic constituents. Planta Medica 1988; 54(2):101-106.
- Keller K, Hansel R, & Chandler RFKeller K, Hansel R, & Chandler RF (Eds): Adverse Effects of Herbal Drugs, 1, Springer-Verlag, Berlin, Germany, 1993.
- Sourgens H, Winterhoff H, Gumbinger HG, et al: Antihormonal effects of plant extracts. TSH- and prolactin-suppressing properties of Lithospermum officinale and other plants. Planta Med 1982; 45:77-86. DOI
Keep reading about Liothyronine
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