Bugle Weed
Quick Facts
- What it is: A North American mint-family herb, used in folk practice to calm an overactive thyroid and ease breast pain.
- Main uses: Mild overactive thyroid, alongside medical care, Palpitations linked to the thyroid, Breast pain and tension
- Active ingredients: Rosmarinic acid, Lithospermic acid, Caffeic acid, Flavonoids, Tannins
- Forms: Dried herb tea, Tincture, Fluid extract, Capsules
- Time to effect: Weeks, if anything at all
- Side effects: Usually mild, but it can push thyroid hormones too low or flare back when stopped.
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What is Bugle Weed?
What is bugleweed?
Bugleweed is a small mint-family plant from North America. Today it is sold mostly for an overactive thyroid. The thyroid is the gland in your neck that sets your body's speed.
This is not a gentle everyday tea. It appears to act on thyroid hormones, which is a drug-like effect. Thyroid disease needs blood tests and medical care, not self-treatment.
You may also see it sold as water horehound or sweet bugle. It is not common horehound. It is also not the garden plant bugle (Ajuga reptans).
Two close cousins are often sold under the same name. These are Lycopus europaeus (gypsywort) and Lycopus americanus. Most of the small amount of human research used the European one.
The honest verdict: human evidence is thin and mixed. One small placebo-controlled trial found only modest changes. Long traditional use is not proof that a remedy works, and it is not proof that it is safe.
How does Bugle Weed work?
How is bugleweed thought to work?
Almost all of what we know comes from lab and animal work, not from people.
In animal studies, extracts lowered thyroid hormone levels. They also lowered TSH. TSH is the brain's signal that tells the thyroid to get busy.
In test-tube studies, plant acids from bugleweed appear to bind TSH and block it at the gland. The same work suggests the herb may slow the change of T4 into T3, the more active hormone.
These acids seem to act only after they oxidise, which means after they react with air. That may be one reason product strength varies so much.
Other test-tube work suggests it may block the antibodies that drive Graves' disease (an immune illness that makes the thyroid overactive). Whether that happens in a living person is not established.
Lab and animal studies also point to a small drop in prolactin. Prolactin is the hormone that drives milk-making. That is why the herb was used for breast pain, and why it is avoided when breastfeeding.
In people, one small trial of the European species found more thyroid hormone leaving the body in urine. Resting pulse fell slightly in people with more symptoms. Blood hormone levels barely moved.
Nothing here shows that bugleweed treats the cause of an overactive thyroid. It does not shrink a goitre (a swollen thyroid) and it does not replace thyroid drugs.
What forms does Bugle Weed come in?
What forms does bugleweed come in?
The dried above-ground parts are used. The root is not.
- Loose dried herb for tea or infusion - Tincture in alcohol, often made from the fresh plant - Fluid extract, which is stronger than tincture - Capsules or tablets of powdered herb - Blended "thyroid support" formulas
American practice has long favoured the fresh-plant tincture. Older writers claimed the dried herb lost strength quickly. That claim has not been tested in a modern way.
Blended products are the biggest problem for a reader. They often mix bugleweed with lemon balm, motherwort, kelp or iodine. Kelp and iodine push the thyroid the opposite way, so the blend may work against itself.
Check the label for the full Latin name. If it only says "bugleweed", you cannot tell which species you have.
Where it comes from:
Where does bugleweed come from?
Nineteenth-century Eclectic physicians in the United States were its main users. The Eclectics were doctors who built their practice around plant medicines.
Their texts, including King's American Dispensatory, listed it as a mild sedative. They gave it for a racing or pounding heart. They also gave it for coughs and for blood coughed up from the lungs, in the days before tuberculosis could be treated.
Those lung uses are not supported today and have been dropped.
German herbal practice took the plant up in the twentieth century, mostly using the European species. The German Commission E, an expert panel that reviewed herbs in the 1980s, wrote a monograph on it. That monograph covered mild thyroid overactivity with nervous symptoms, and breast pain and tension.
That panel reviewed tradition and early data. It did not run trials. A monograph is a review, not proof of benefit.
Who should avoid Bugle Weed?
- Never use bugleweed instead of medical care for an overactive thyroid; untreated, it can damage your heart and bones.
- Do not use it if you have an underactive thyroid (a thyroid that makes too little hormone).
- Do not use it if you take levothyroxine or any other thyroid hormone tablet.
- Do not use it if you take carbimazole, methimazole or propylthiouracil, unless your doctor is supervising.
- Do not use it if you have a goitre (a swollen thyroid) without a known overactive thyroid.
- Do not use it before or during a radioactive iodine scan or treatment; tell the clinic you have taken it.
- Do not use it if you are pregnant or trying to conceive.
- Do not use it if you are breastfeeding; it may cut your milk supply.
- Do not give it to children.
- Avoid it if you are allergic to mint-family plants such as mint, sage or lemon balm.
- Do not stop it suddenly after weeks of use; ask your doctor how to come off it.
When should you see a doctor?
When to see a doctor
Get urgent help, the same day, if you have:
- A resting pulse that stays very fast, or a pounding, irregular heartbeat - Chest pain or bad shortness of breath - Fever with confusion, agitation or vomiting, which can signal a thyroid crisis
Book a normal appointment if you notice:
- New swelling at the front of your neck - Growing tiredness, feeling cold, constipation or weight gain - Low mood, dry skin or hair loss - Eye changes, such as bulging or double vision
Stop the herb and speak to your doctor if your symptoms flare after you stop taking it. Tell every doctor you see that you are using it, especially before thyroid tests or surgery.
Is Bugle Weed legal where you live?
In the United States it is sold as a dietary supplement, so it is not reviewed for benefit before sale. In Germany it has a Commission E monograph as a herbal medicine. In the UK, Canada and Australia it is sold as a herbal product, and rules differ by country.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
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