Table of Contents
- Introduction
- What Is Ashwagandha?
- How the Thyroid Works: A Brief Overview
- Can Ashwagandha Cause Thyroid Issues?
- The Blue Horizon Method: A Responsible Path
- Understanding Our Thyroid Testing Tiers
- Practical Logistics of Testing
- Who Should Avoid Ashwagandha?
- Talking to Your GP About Your Results
- The Importance of Quality and Dosage
- Summary of Key Takeaways
- FAQ
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. Known as an "adaptogen," this ancient herb 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 "mystery 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, there is a complex relationship between this herb and the butterfly-shaped gland in your neck. For some, ashwagandha may provide 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. We are a doctor-led team established in 2009, and our goal is to complement the care you receive from your GP by providing detailed insights into your biochemistry. We don't believe in chasing a single "miracle" supplement or one isolated marker. Instead, we advocate for a phased, clinically responsible journey—what we call the Blue Horizon Method.
This involves consulting your GP first to rule out underlying causes, tracking your lifestyle and symptoms, and only then using structured blood testing to guide a more productive conversation with a healthcare professional. In this article, we will explore the science behind ashwagandha, how it interacts with thyroid hormones, and what you need to know before adding it to your daily routine.
What Is Ashwagandha?
Ashwagandha (Withania somnifera) is a cornerstone of Ayurvedic medicine, a traditional healing system from India that dates back thousands of years. It is often referred to as "Indian Ginseng" or "Winter Cherry." The name itself comes from Sanskrit, meaning "smell of the horse," which refers both 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. This means it is believed to help the body maintain "homeostasis"—a state of internal balance—even when faced with physical or emotional stress. It does this primarily by modulating the hypothalamic-pituitary-adrenal (HPA) axis, which controls our stress response and the release of cortisol.
While many people take it to help with anxiety or insomnia, ashwagandha is biologically active. It contains compounds called withanolides, which have anti-inflammatory and antioxidant properties. However, because it is biologically active, it can influence other hormonal systems in the body, including the thyroid gland.
How the Thyroid Works: A Brief Overview
To understand how a supplement might cause "issues," we first need to understand the standard operation of the thyroid gland. The thyroid is part of the endocrine system and produces hormones that regulate your metabolism, heart rate, and body temperature.
The process is managed by a feedback loop involving the brain and the thyroid:
- TSH (Thyroid Stimulating Hormone): Produced by the pituitary gland in the brain, TSH is the "messenger." When thyroid hormone levels are low, the brain releases more TSH to tell the thyroid to work harder.
- Free T4 (Thyroxine): This is the primary hormone produced by the thyroid. It is largely inactive and must be converted into T3 to be used by the body's cells.
- Free T3 (Triiodothyronine): This is the active form of the hormone. It is responsible for the "engine room" functions of your metabolism.
When this loop is disrupted, you may experience hypothyroidism (an underactive thyroid, where the engine is running too slowly) or hyperthyroidism (an overactive thyroid, where the engine is red-lining).
Can Ashwagandha Cause Thyroid Issues?
The relationship between ashwagandha and the thyroid is primarily stimulatory. Research suggests that ashwagandha can increase the production of T4 and T3 while lowering TSH.
For someone with subclinical hypothyroidism (where TSH is slightly high but T4 is still in the normal range), this stimulatory effect can sometimes be beneficial, helping to "nudge" the thyroid back into a normal rhythm. However, this same mechanism is exactly why it can cause issues for others.
The Risk of Thyrotoxicosis
One of the most concerning potential issues is thyrotoxicosis. This is a clinical state where there is too much thyroid hormone in the body. While rare, there have been documented cases—including in patients here in the UK—of individuals developing symptoms of an overactive thyroid after taking ashwagandha.
In these cases, the herb stimulates the thyroid to produce such high levels of hormones that the person experiences:
- 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
Another issue is that ashwagandha may "mask" or complicate the management of autoimmune thyroid conditions like Hashimoto’s thyroiditis or Graves’ disease. Because ashwagandha 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.
The Blue Horizon Method: A Responsible Path
Before you decide to take ashwagandha—or if you are already taking it and feel "off"—we recommend following a structured approach to your health.
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 thyroid disease or other common causes of fatigue and anxiety, such as anaemia or vitamin deficiencies. 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. Note down:
- The timing of your symptoms: Do palpitations happen shortly after taking your supplement?
- Lifestyle factors: Are you sleeping enough? Is your stress unusually high?
- Patterns: Does your energy dip at specific times of the day?
- Supplement Log: Exactly how much ashwagandha are you taking, and what is the concentration of withanolides?
3. Consider Targeted Testing
If your GP has ruled out major illness but you still feel "stuck," or if you want a more detailed "snapshot" of your thyroid health to guide your next conversation with a professional, a private blood test can be a valuable tool.
Unlike standard tests that might only look at TSH, our panels look at the "bigger picture," including cofactors that influence how you actually feel.
Understanding Our Thyroid Testing Tiers
At Blue Horizon, we offer a range of thyroid tests designed to provide different levels of insight. We don't believe in a "one size fits all" approach. To see the full range, start with our thyroid blood tests collection.
Most providers do not include these, but we believe they are essential. Cortisol is your primary stress hormone; if it is chronically high, it can interfere with how your body converts T4 into the active T3. Magnesium is a vital cofactor for hundreds of enzymatic reactions, including thyroid hormone production.
Bronze Thyroid Check
This is our focused starting point. It includes the base thyroid markers: TSH, Free T4, and Free T3, alongside the Blue Horizon Extras (Magnesium and Cortisol). This is ideal if you want to see if your "engine" is running at the right speed and if stress (Cortisol) might be a factor. You can view the full details on our Thyroid Premium Bronze page.
Silver Thyroid Check
The Silver tier includes everything in Bronze but adds Thyroid Peroxidase Antibodies (TPOAb) and Thyroglobulin Antibodies (TgAb). These are autoimmune markers. Checking these is crucial because many thyroid issues in the UK are caused by the immune system attacking the thyroid. Knowing your antibody status helps you understand the cause of a thyroid imbalance, not just the symptoms. Learn more on the Thyroid Premium Silver page.
Gold Thyroid Check
The Gold tier is a broader health snapshot. It includes everything in Silver plus:
- Ferritin (Iron stores): Low iron can mimic thyroid symptoms.
- Folate and Active Vitamin B12: Essential for energy and nervous system health.
- C-Reactive Protein (CRP): A marker of systemic inflammation.
- Vitamin D: Vital for immune regulation and bone health.
- This tier is excellent for those with "mystery fatigue" who want to rule out common nutrient deficiencies alongside thyroid issues.
If you want the more complete version, take a look at the Thyroid Premium Gold profile.
Platinum Thyroid Check
This is our most comprehensive thyroid and metabolic profile. It includes everything in the Gold tier plus:
- Reverse T3: Think of this as the "brake" on your metabolism. If your body is under extreme stress, it may produce more Reverse T3 to slow you down.
- HbA1c: A marker of your average blood sugar levels over the last few months.
- Full Iron Panel: Including Transferrin Saturation, TIBC, and UIBC.
- The Platinum test provides the most detailed view of how your thyroid interacts with your wider metabolism.
For the full metabolic picture, see the Thyroid Premium Platinum page.
Practical Logistics of Testing
If you decide to pursue testing to see how ashwagandha or other factors are affecting your health, here is what you need to know about the process:
- Sample Timing: We generally recommend a 9am sample. Thyroid hormones and cortisol both follow a "circadian rhythm," meaning they fluctuate throughout the day. A 9am sample ensures consistency and aligns with the natural peak of these hormones, making your results easier to interpret.
- Collection Methods: For our Bronze, Silver, and Gold tiers, you have flexibility. You can choose a fingerprick sample at home, use a Tasso device (which draws blood from the upper arm), visit a local clinic, or even arrange for a nurse to visit your home. If you prefer an at-home option, read more about our finger-prick blood test kits.
- Professional Blood Draws: Our Platinum tier is so comprehensive that it requires a larger volume of blood. Therefore, it requires a professional venous blood draw, which can be done at a clinic or via a home nurse visit. If that suits you better, see our nurse home visit service.
Who Should Avoid Ashwagandha?
While ashwagandha is generally considered safe for healthy individuals for short-term use, there are several groups who should exercise extreme caution:
- Those with Hyperthyroidism: If you already have an overactive thyroid or Graves’ disease, ashwagandha’s stimulatory effect could be dangerous.
- Pregnant or Breastfeeding Women: There is insufficient evidence to guarantee safety, and some traditional sources suggest it may have abortifacient properties at very high doses.
- People on Thyroid Medication: If you take levothyroxine, ashwagandha may increase your hormone levels further, potentially requiring a medication adjustment. Never adjust your prescription medication based on a private blood test; always work with your GP or endocrinologist.
- Those with Autoimmune Diseases: Because it can "boost" the immune system, it may exacerbate conditions like Lupus, Multiple Sclerosis, or Rheumatoid Arthritis.
- Upcoming Surgery: Ashwagandha can have a sedative effect on the central nervous system, which may interact with anaesthesia. Most professionals recommend stopping it at least two weeks before surgery.
Talking to Your GP About Your Results
If you choose to take a Blue Horizon test, your results will be delivered in a clear, structured report. However, it is important to remember that a blood test is not a diagnosis. It is a snapshot in time.
When you take your results to your GP, use them to facilitate a better conversation. You might say: "I’ve been feeling quite fatigued and anxious, and I noticed my Free T3 was at the very low end of the range, while my Cortisol was quite high. I was wondering if we could look into how stress might be impacting my thyroid function?"
This collaborative approach is much more effective than self-diagnosing or demanding specific treatments. Your GP can look at your results alongside your medical history, any medications you are taking, and your physical symptoms to decide on the best clinical path forward.
If you want a deeper explanation of the process, the guide on how to have your thyroid tested is a useful next step.
The Importance of Quality and Dosage
If you and your healthcare professional decide that ashwagandha is appropriate for you, quality matters. Supplements in the UK are not regulated as strictly as medicines.
- Standardisation: Look for products that list a specific percentage of "withanolides."
- Dosage: Most clinical studies use between 300mg and 600mg of root extract daily. Taking massive doses increases the risk of side effects like diarrhoea, nausea, and the thyroid issues discussed above.
- Fillers: Be wary of cheap supplements with unnecessary fillers or additives that could cause digestive upset, which you might then mistake for a thyroid symptom.
If you are still deciding what to ask for, our guide on how to test thyroid function explains the different markers and testing options in more detail.
Summary of Key Takeaways
Ashwagandha is a powerful herb with a long history of use, but "natural" does not mean "side-effect free." Its ability to stimulate the thyroid can be a double-edged sword.
- It can raise thyroid hormones: This may help some with an underactive thyroid but can lead to thyrotoxicosis in others.
- Symptoms matter: If you feel "off"—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 in a diary, and use targeted testing (like our Gold or Platinum tiers) if you need a deeper look at your biochemistry.
- Context is key: Don't look at thyroid markers in isolation. Markers like Magnesium and Cortisol (included in all our tests) provide essential context for how you actually feel.
If you want a broader explanation of why these markers matter, read Thyroid Tests with Cortisol and Magnesium. You can also learn more about the people behind the service on our About Us page.
Your health is a journey, not a quick fix. By taking a measured, doctor-led approach, you can ensure that the supplements you take are supporting your well-being rather than sabotaging it. You can view current pricing and more details on our thyroid testing page to help you decide which level of insight is right for you.
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.
Thyroid blood tests
Thyroid Premium Bronze
Thyroid Premium Silver
Thyroid Premium Gold
