Introduction
If you have spent any time browsing the wellness aisles of a UK pharmacy or scrolling through health-focused social media, you have almost certainly encountered ashwagandha. This ancient "adaptogen" is frequently praised for its ability to help the body manage stress, improve sleep, and boost energy levels. However, as its popularity grows, so do the questions regarding its safety, particularly for those with symptoms like unexplained fatigue, a racing heart, or sudden weight changes.
The central question many people are now asking is: can ashwagandha cause thyroid issues? While many users find it helpful for stress, research suggests that ashwagandha can increase the production of T4 and T3 while lowering TSH. For some, this provides a welcome boost to an underactive thyroid; for others, it can push the system into overdrive, leading to potentially serious health complications.
At Blue Horizon, we believe that the best health decisions are made when you see the bigger picture. Established in 2009, our doctor-led team complements the care you receive from your GP by providing detailed insights into your biochemistry. We advocate for a phased, clinically responsible journey—what we call the Blue Horizon Method. This involves consulting your GP first, tracking your lifestyle and symptoms, and then using structured blood testing to guide a productive conversation with a healthcare professional.
Quick Answer: Ashwagandha can significantly affect thyroid hormones, often increasing T4 and T3 production while lowering TSH. While this may support those with subclinical hypothyroidism, it can be risky for individuals with hyperthyroidism or those already taking thyroid medication.
What Is Ashwagandha?
Ashwagandha (Withania somnifera) is a cornerstone of Ayurvedic medicine, often referred to as "Indian Ginseng." The name comes from Sanskrit, meaning "smell of the horse," referring to its unique earthy scent and the traditional belief that it provides the strength and stamina of a stallion.
In modern herbalism, ashwagandha is classified as an adaptogen. It is believed to help the body maintain homeostasis by modulating the hypothalamic-pituitary-adrenal (HPA) axis, which controls our stress response and cortisol release. While many take it for anxiety or insomnia, ashwagandha contains biologically active compounds called withanolides that can influence other hormonal systems, including the thyroid gland.
How the Thyroid Works: A Brief Overview
The thyroid gland produces hormones that regulate your metabolism, heart rate, and body temperature. This process is managed by a feedback loop involving the brain and the thyroid:
- TSH (Thyroid Stimulating Hormone): Produced by the pituitary gland, TSH acts as the messenger. When thyroid hormone levels are low, the brain releases more TSH to tell the thyroid to work harder.
- Free T4 (Thyroxine): The primary hormone produced by the thyroid; it is largely inactive and must be converted into T3 to be used by cells.
- Free T3 (Triiodothyronine): The active form of the hormone responsible for your metabolic "engine room."
When this loop is disrupted, you may experience hypothyroidism (underactive) or hyperthyroidism (overactive).
Can Ashwagandha Cause Thyroid Issues?
The relationship between ashwagandha and the thyroid is primarily stimulatory. Research indicates it can increase T4 and T3 production while lowering TSH.
For someone with subclinical hypothyroidism (high TSH but normal T4), this effect can sometimes be beneficial. However, this same mechanism is why it causes issues for others.
The Risk of Thyrotoxicosis
One of the most concerning potential issues is thyrotoxicosis, a state where there is too much thyroid hormone in the body. While rare, there have been documented cases in the UK of individuals developing symptoms of an overactive thyroid after taking ashwagandha.
In these cases, the herb stimulates the thyroid to produce excessive hormones, leading to:
- Palpitations or a rapid heartbeat (tachycardia)
- Anxiety and irritability
- Unexplained weight loss
- Heat intolerance and excessive sweating
- Tremors in the hands
Urgent Safety Note: If you experience sudden or severe symptoms such as difficulty breathing, swelling of the lips, face, or throat, or a sudden collapse, you must seek urgent medical attention immediately by calling 999 or visiting your nearest A&E.
Masking Underlying Autoimmunity
Ashwagandha may also complicate the management of autoimmune thyroid conditions like Hashimoto’s thyroiditis or Graves’ disease. Because it can stimulate the immune system, there is a theoretical risk that it could exacerbate an autoimmune flare-up, even while it temporarily improves hormone numbers on a lab report.
Quick Summary:
- Hormonal Impact: Ashwagandha typically raises T4/T3 levels and lowers TSH.
- Who is at Risk: Individuals with hyperthyroidism, Graves' disease, or those on thyroid medication should be extremely cautious.
- Listen to Symptoms: Anxiety, tremors, and heart palpitations are key warning signs of overstimulation.
- Testing Context: A single marker like TSH doesn't tell the whole story; comprehensive testing is needed to see the full metabolic picture.
The Blue Horizon Method: A Responsible Path
Before starting ashwagandha—or if you are taking it and feel "off"—we recommend a structured approach.
1. Consult Your GP First
Always discuss new symptoms or supplements with your GP. They can perform standard NHS thyroid function tests to rule out primary disease or other causes of fatigue like anaemia. It is vital to rule out clinical conditions before attempting to "optimise" with herbs.
2. Use a Structured Self-Check
Keep a diary for two to four weeks noting:
- Symptom Timing: Do palpitations occur shortly after taking the supplement?
- Lifestyle Factors: Sleep quality and current stress levels.
- Supplement Log: Your exact dosage and the concentration of withanolides.
3. Consider Targeted Testing
If you still feel "stuck" after seeing your GP, or want a more detailed snapshot of your thyroid health, a private blood test can be a valuable tool. Our panels look at the "bigger picture," including cofactors like cortisol and magnesium.
Understanding Our Thyroid Testing Tiers
At Blue Horizon, we offer a range of thyroid blood tests collection designed to provide different levels of insight.
| Profile | Core Thyroid & Stress Markers | Autoimmune Antibodies | Nutrients & Metabolic Markers |
|---|---|---|---|
| Thyroid Premium Bronze | TSH, Free T4, Free T3, Magnesium, Cortisol | - | - |
| Thyroid Premium Silver | TSH, Free T4, Free T3, Magnesium, Cortisol | TPOAb, TgAb | - |
| Thyroid Premium Gold | TSH, Free T4, Free T3, Magnesium, Cortisol | TPOAb, TgAb | Ferritin, Folate, Active B12, CRP, Vitamin D |
| Thyroid Premium Platinum | TSH, Free T4, Free T3, Magnesium, Cortisol | TPOAb, TgAb | Ferritin, Folate, B12, CRP, Vitamin D, Reverse T3, HbA1c, Full Iron Panel |
Practical Logistics of Testing
If you decide to pursue testing, keep the following logistics in mind:
- Sample Timing: We recommend a 9am sample. Thyroid hormones and cortisol follow a circadian rhythm; a 9am sample ensures consistency and aligns with the natural peak of these hormones.
- Collection Methods: For Bronze, Silver, and Gold tiers, you can choose a fingerprick sample at home, use a Tasso device, visit a local clinic, or arrange a home nurse visit. Learn more about our finger-prick blood test kits.
- Professional Blood Draws: The Platinum tier requires a larger volume of blood and must be collected via a professional venous blood draw at a clinic or via a nurse home visit service.
Who Should Avoid Ashwagandha?
While generally safe for short-term use in healthy individuals, several groups should exercise extreme caution:
- Those with Hyperthyroidism: If you have an overactive thyroid or Graves’ disease, the herb's stimulatory effect could be dangerous.
- Pregnant or Breastfeeding Women: There is insufficient evidence for safety; some sources suggest it may have abortifacient properties at high doses.
- People on Thyroid Medication: If you take levothyroxine, ashwagandha may increase your hormone levels further. Never adjust your prescription medication based on a private blood test; always work with your GP or endocrinologist.
- Those with Autoimmune Diseases: It may exacerbate conditions like Lupus, Multiple Sclerosis, or Rheumatoid Arthritis by boosting the immune system.
- Upcoming Surgery: Its sedative effect may interact with anaesthesia. Stop use at least two weeks before surgery.
Talking to Your GP About Your Results
A blood test is a snapshot in time, not a diagnosis. Use your report to facilitate a better conversation with your doctor. You might say:
"I’ve been feeling fatigued and anxious, and I noticed my Free T3 was at the low end of the range while my Cortisol was high. Could we look into how stress might be impacting my thyroid function?"
This collaborative approach is more effective than self-diagnosing. For a deeper explanation, see our guide on how to have your thyroid tested.
The Importance of Quality and Dosage
If you and your healthcare professional decide ashwagandha is right for you, quality is paramount:
- Standardisation: Look for products listing a specific percentage of "withanolides."
- Dosage: Clinical studies typically use 300mg to 600mg of root extract daily. Massive doses increase the risk of nausea, diarrhoea, and thyroid issues.
- Fillers: Avoid supplements with unnecessary additives that could cause digestive upset.
For more detail on markers, read our guide on how to test thyroid function.
Summary of Key Takeaways
Ashwagandha is a powerful herb, but its ability to stimulate the thyroid is a double-edged sword.
- It can raise thyroid hormones: This helps some with an underactive thyroid but can lead to thyrotoxicosis in others.
- Symptoms matter: If you feel shaky, anxious, or have a racing heart, stop the supplement and speak to a doctor.
- The Blue Horizon Method: Start with your GP, track your symptoms, and use targeted testing (like our Gold or Platinum tiers) for a deeper look at your biochemistry.
- Context is key: Don't look at thyroid markers in isolation. Markers like Magnesium and Cortisol provide essential context for how you actually feel. Read more about Thyroid Tests with Cortisol and Magnesium.
Learn more about our team on the About Us page.
FAQ
Can ashwagandha cause an overactive thyroid?
Yes, for some individuals, ashwagandha can stimulate the thyroid gland to produce excessive amounts of T4 and T3 hormones. This can lead to a state called thyrotoxicosis, where the body has more thyroid hormone than it can handle, resulting in symptoms like palpitations, anxiety, and weight loss. If you have a history of hyperthyroidism, you should avoid ashwagandha unless specifically advised by your doctor.
Is it safe to take ashwagandha if I am already on levothyroxine?
You should be very cautious. Because ashwagandha can naturally increase thyroid hormone levels, taking it alongside levothyroxine (synthetic T4) could potentially cause your levels to become too high. This might lead to symptoms of hyperthyroidism. If you wish to try ashwagandha while on medication, it is essential to discuss it with your GP or endocrinologist first and monitor your levels closely.
How long does it take for ashwagandha to affect the thyroid?
In most clinical studies, changes in thyroid hormone levels were observed after approximately eight weeks of daily supplementation. However, some people may feel the effects—or side effects—much sooner. If you start a new supplement and begin to feel "off" within the first few days or weeks, it is worth noting these changes in a symptom diary and consulting a professional.
Should I stop taking ashwagandha before a thyroid blood test?
If you want to know what your "baseline" thyroid function is without the influence of the herb, it is often recommended to stop taking it for at least two weeks before a test. However, if you want to see how the ashwagandha is currently affecting your levels, you would continue taking it as usual. Always inform your GP or the laboratory about any supplements you are taking so they can interpret your results accurately.
