Introduction
In the search for a natural remedy to combat the stresses of modern life, many people across the UK have turned to ashwagandha. You might have seen it on the shelves of high-street health shops or heard it recommended by a friend as a "miracle" for anxiety and fatigue. However, while this ancient herb is celebrated for its ability to help the body manage stress, its impact on the delicate balance of the thyroid gland is often overlooked.
For some, ashwagandha provides a much-needed boost, but for others, it can lead to unexpected "mystery symptoms"—such as a racing heart, sudden weight loss, or an overwhelming sense of jitteriness. If you have been taking this supplement and have noticed changes in how you feel, or if you are considering starting it while managing a known thyroid condition, it is vital to understand the relationship between this herb and your hormones.
This article will explore the clinical evidence surrounding ashwagandha and thyroid function, the potential risks of thyrotoxicosis, and how the herb may interact with common medications like levothyroxine. We will also guide you through the responsible way to monitor your health if you suspect your supplements are affecting your thyroid.
At Blue Horizon, we believe that health decisions should be based on a complete picture. Our approach, the Blue Horizon Method, prioritises clinical safety and informed conversations with your GP. We recommend a phased journey: first, consult your GP to rule out underlying causes; second, use a structured self-check approach to track your symptoms and lifestyle; and third, consider a targeted blood test only if you need a clearer "snapshot" to guide your professional care.
Understanding the Thyroid Gland
To understand whether ashwagandha causes thyroid issues, we must first look at how the thyroid operates. This butterfly-shaped gland, situated at the base of your neck, acts as the master controller of your metabolism. It influences almost every cell in your body, from how fast your heart beats to how quickly you burn calories.
The thyroid does not work in isolation. It is part of a complex feedback loop known as the Hypothalamic-Pituitary-Thyroid (HPT) axis.
- TSH (Thyroid Stimulating Hormone): This is a messenger sent from the pituitary gland in the brain. Think of it as a thermostat. If your body needs more energy, the pituitary releases more TSH to "tell" the thyroid to work harder. If there is plenty of thyroid hormone in the blood, TSH levels drop.
- Free T4 (Thyroxine): This is the primary hormone produced by the thyroid gland. It is relatively inactive and acts as a reservoir, waiting to be converted into the active form.
- Free T3 (Triiodothyronine): This is the active form of the hormone. It is what your cells actually use to produce energy and regulate metabolism.
When this system is in balance, you generally feel energetic and well. However, if the gland becomes overactive (hyperthyroidism) or underactive (hypothyroidism), a cascade of symptoms can follow.
For a practical overview of thyroid markers and testing options, read this guide to thyroid function tests and key results.
What is Ashwagandha?
Ashwagandha (Withania somnifera) is a cornerstone of Ayurvedic medicine, often referred to as "Indian Ginseng." It is classified as an adaptogen. In plain English, an adaptogen is a substance that helps your body "adapt" to physical or emotional stress by modulating the endocrine system.
Most people take ashwagandha because it is believed to lower cortisol, the body’s primary stress hormone. When we are chronically stressed, our cortisol levels remain high, which can interfere with various bodily functions, including sleep, immunity, and—crucially—thyroid function.
Does Ashwagandha Cause Thyroid Issues?
The question of whether ashwagandha "causes" thyroid issues is nuanced. For most healthy individuals, it is considered safe. However, because ashwagandha is biologically active, it can change the way your thyroid behaves.
The Risk of Thyrotoxicosis
The most significant concern for some individuals is thyrotoxicosis. This is a condition where there is too much thyroid hormone (T3 and T4) circulating in the bloodstream. Clinical case reports have identified instances where individuals taking ashwagandha extract developed symptoms of an overactive thyroid, which resolved only after they stopped taking the supplement.
In these cases, the herb appears to over-stimulate the thyroid gland. This can lead to:
- An unusually fast or irregular heartbeat (palpitations).
- 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, chest pain, a very rapid heartbeat, or swelling of the lips and face, seek urgent medical attention immediately by calling 999 or visiting your local A&E.
Painless Thyroiditis
There are also rare reports of ashwagandha-induced "painless thyroiditis." This occurs when the thyroid gland becomes inflamed (though not necessarily painful) and "leaks" stored hormones into the blood. This creates a temporary state of hyperthyroidism, often followed by a period of low thyroid function as the gland recovers.
Potential Benefits for Underactive Thyroid
Paradoxically, the very mechanism that makes ashwagandha risky for some may make it helpful for others. Some studies suggest that for people with subclinical hypothyroidism (a state where TSH is slightly high but T4 is still in the normal range), ashwagandha may help "nudge" the thyroid into a more active state, lowering TSH and increasing T4 levels.
However, this should never be used as a replacement for prescribed medication without strict medical supervision.
Interactions with Thyroid Medication
If you are already being treated for a thyroid condition, such as Hashimoto’s disease or primary hypothyroidism, you must be particularly cautious.
In the UK, the standard treatment for an underactive thyroid is levothyroxine. Because ashwagandha may naturally increase thyroid hormone production, taking it alongside levothyroxine can potentially lead to an "over-treatment" effect. This means your levels could rise too high, pushing you into a hyperthyroid state even though your original problem was an underactive thyroid.
Furthermore, ashwagandha may interact with:
- Sedatives and Sleep Medication: Since ashwagandha has a calming effect, it can amplify the effects of medications used for anxiety or insomnia.
- Immunosuppressants: As the herb can stimulate the immune system, it may interfere with medications taken for autoimmune conditions.
- Blood Sugar Medication: Ashwagandha may lower blood sugar, which could be problematic if you are already taking insulin or other diabetes medications.
The Blue Horizon Method: A Step-by-Step Approach
If you are concerned about your thyroid health or are unsure if your supplements are suitable for you, we recommend following our structured approach.
Step 1: Consult Your GP First
Always talk to your GP before starting or stopping a supplement like ashwagandha, especially if you have a history of thyroid issues. Your GP can perform standard NHS thyroid function tests and review your current medications. It is important to rule out other causes for your symptoms, such as anaemia or vitamin deficiencies, which can often mimic thyroid problems.
Step 2: Use a Structured Self-Check
Before moving to private testing, track your symptoms over a period of 2 to 4 weeks. Note down:
- Energy levels: When do you feel most tired?
- Mood changes: Are you feeling unusually anxious or "wired"?
- Physical changes: Have you noticed changes in your hair, skin, or weight?
- Supplement timing: Record exactly when you take ashwagandha and at what dose.
- Lifestyle factors: Are you getting enough sleep? Has your stress level changed?
This diary will be incredibly useful for your GP or consultant and helps you see the "bigger picture" of your health.
Step 3: Consider Structured Private Testing
If you have consulted your GP and still feel "stuck," or if you want a more detailed snapshot of your thyroid health to share with a professional, a private blood test can provide additional data.
At Blue Horizon, we offer a tiered range of thyroid blood tests. These are designed to be "premium" because they include markers that go beyond the standard TSH and T4 checks. Specifically, all our thyroid tiers include magnesium and cortisol.
- Magnesium: An essential mineral that plays a role in converting T4 into the active T3.
- Cortisol: Known as the stress hormone, it has a direct relationship with thyroid function. Understanding your cortisol levels helps provide context for your thyroid results.
Choosing the Right Thyroid Test
When investigating the impact of supplements like ashwagandha, different people require different levels of detail.
Thyroid Bronze
This is our focused starting point. It measures the base thyroid markers: TSH, Free T4, and Free T3, alongside the Blue Horizon Extras (magnesium and cortisol). This is useful if you simply want to see if your active hormone levels (T3) are within the expected range. You can review the full inclusions in the Thyroid Premium Bronze profile.
Thyroid Silver
The Silver tier includes everything in the Bronze test but adds Thyroid Peroxidase Antibodies (TPOAb) and Thyroglobulin Antibodies (TgAb). These markers help identify if there is an autoimmune component, such as Hashimoto’s disease, where the immune system attacks the thyroid. Ashwagandha can sometimes stimulate the immune system, so knowing your antibody status is valuable. See the Thyroid Premium Silver profile for the full panel.
Thyroid Gold
This provides a broader health snapshot. In addition to the Silver markers, it includes Ferritin, Folate, Vitamin B12, Vitamin D, and CRP (a marker of inflammation). This is ideal if you are feeling fatigued and want to ensure that your symptoms aren't being caused by common nutrient deficiencies or low-level inflammation. The Thyroid Premium Gold profile includes the full list of markers.
Thyroid Platinum
Our most comprehensive profile. It includes everything in the Gold tier plus Reverse T3, HbA1c (for blood sugar), and a full iron panel. Reverse T3 is sometimes measured to see if the body is "clearing" thyroid hormone effectively, which can be relevant during times of significant stress or illness. You can explore the Thyroid Premium Platinum profile for its complete inclusions.
Note on Sample Collection: The Bronze, Silver, and Gold tests can be completed via a simple fingerprick sample at home, or with a professional visit. The Platinum test requires a larger volume of blood, so it must be performed via a professional venous blood draw at a clinic or with a nurse home visit. We recommend taking thyroid samples at 9 am to ensure consistency with natural daily hormone fluctuations.
For further guidance on choosing between testing options, read how to test your thyroid.
Interpreting Your Results Responsibly
It is vital to remember that blood test results are a "snapshot" in time. They are not a diagnosis. A "normal" result does not necessarily mean nothing is wrong, and an "abnormal" result does not always mean you have a disease.
When you receive your Blue Horizon report, it will provide your levels alongside reference ranges. However, these results should always be discussed with your GP or a qualified endocrinologist. You should never adjust your prescription medication based on a private test result alone.
If your results suggest that your thyroid is becoming overactive while taking ashwagandha, your doctor may suggest stopping the supplement and re-testing after a few weeks to see if the levels return to your baseline.
Who Should Avoid Ashwagandha?
While many people use ashwagandha without issue, certain groups should be extremely cautious or avoid it entirely:
- Those with Hyperthyroidism: If you already have an overactive thyroid or Graves’ disease, ashwagandha could exacerbate your symptoms and lead to thyrotoxicosis.
- Pregnant or Breastfeeding Women: There is insufficient evidence regarding the safety of ashwagandha during pregnancy, and some traditional uses suggest it may even be harmful to the pregnancy.
- Those Scheduled for Surgery: Because ashwagandha can affect the central nervous system and interact with anaesthesia, it is usually recommended to stop taking it at least two weeks before a scheduled operation.
- People with Autoimmune Diseases: Because it can stimulate the immune system, those with conditions like lupus, multiple sclerosis, or rheumatoid arthritis should consult their specialist first.
Practical Scenarios
Scenario A: The "Wired but Tired" Feeling
Imagine you have been taking ashwagandha for six weeks to help with work stress. Lately, you’ve noticed that while you feel less "worried," you also feel physically jittery, your heart is racing in the evenings, and you’re struggling to sleep.
- Action: This could be a sign of ashwagandha-induced thyrotoxicosis. You should see your GP and consider a Thyroid Bronze or Silver test to check if your Free T3 and Free T4 levels have risen above the normal range.
Scenario B: The Persistent Fatigue
You have an underactive thyroid and take levothyroxine daily. You decide to add ashwagandha to your routine to help with lingering tiredness. After a month, you don't feel any better; in fact, you feel more sluggish and have developed a "brain fog."
- Action: It is possible the supplement is interacting with your medication or that your fatigue is due to something else, like low Vitamin D or B12. A Thyroid Gold test could help identify if nutrient deficiencies are the culprit while also checking your thyroid markers.
Summary of Key Takeaways
- Ashwagandha is biologically active: It is an adaptogen that can lower cortisol but may also stimulate the production of thyroid hormones (T3 and T4).
- Potential for Hyperthyroidism: In some individuals, particularly those with a predisposition, ashwagandha may lead to thyrotoxicosis or thyroiditis.
- Hypothyroidism Nuance: While it may help some people with a mildly underactive thyroid, it should not be used as a self-prescribed treatment.
- Medication Interactions: It can interact with levothyroxine, sedatives, and blood sugar medications.
- The GP-First Rule: Always discuss new symptoms and supplements with your GP first to rule out serious underlying conditions.
- Strategic Testing: If you choose to test privately, use a structured panel like those offered by Blue Horizon to get a fuller picture including magnesium and cortisol.
Conclusion
The relationship between ashwagandha and thyroid function is a prime example of why we believe in "seeing the bigger picture." While herbal supplements are often viewed as "natural" and therefore "harmless," they can have powerful effects on our endocrine system.
If you suspect ashwagandha is causing thyroid issues for you, the most responsible path is to pause, reflect, and seek professional guidance. Start by speaking with your GP about your symptoms. Use a diary to track how you feel, and if you find that you need more detailed data to help guide your clinical conversations, choose a structured blood test that looks at thyroid function alongside key cofactors like cortisol and magnesium.
Good health isn't about finding a single "magic pill"—it’s about understanding how your lifestyle, supplements, and unique biology work together. By taking a phased, medically-led approach, you can navigate your health journey with confidence and clarity.
FAQ
Can I take ashwagandha if I have Hashimoto’s disease?
If you have Hashimoto’s, you should be very cautious. Because ashwagandha can stimulate the immune system and increase thyroid hormone production, it may interfere with your levothyroxine dose or potentially trigger an immune flare-up. It is essential to consult your GP or endocrinologist before adding it to your routine. Monitoring your thyroid antibodies through a Thyroid Silver or Gold test can help provide a baseline for your doctor to review.
How long does it take for ashwagandha to affect thyroid levels?
The impact on thyroid levels can vary. In some clinical studies, changes in TSH and T4 were noted after eight weeks of consistent use. However, some case reports of thyrotoxicosis suggest that symptoms can appear sooner or take much longer depending on the dosage and the individual’s baseline health. If you feel "off" shortly after starting, listen to your body and seek medical advice.
Will stopping ashwagandha reverse thyroid issues?
In many documented cases of ashwagandha-induced thyrotoxicosis or painless thyroiditis, the symptoms and hormone levels returned to normal once the supplement was discontinued. However, this is not a guarantee, especially if there is an underlying autoimmune condition. You should always work with your GP to monitor your recovery and ensure your thyroid function stabilizes.
Why does Blue Horizon include cortisol in thyroid tests?
We include cortisol because the thyroid and the adrenal glands (which produce cortisol) are closely linked through the endocrine system. High or low cortisol levels can significantly impact how your thyroid hormones are used by your cells. Since many people take ashwagandha specifically to manage stress and cortisol, measuring both gives a much clearer picture of how the supplement is affecting your overall hormonal balance. You can view current pricing and details for these panels on our thyroid testing page.
