Your Cart is Empty

May 11, 2023 8 min read

When it comes to hypothyroidism treatment, levothyroxine is undoubtedly the go-to medication for millions of people around the world. This synthetic hormone works wonders in helping individuals manage their underactive thyroid and improve their overall quality of life. However, as with any medication, levothyroxine may cause some side effects, and one of the most commonly reported is diarrhea. But how does levothyroxine lead to diarrhea? And what can you do about it? Here's everything you need to know

Understanding hypothyroidism and levothyroxine

Before we explore the connection between levothyroxine and diarrhea, it's essential to understand what levothyroxine is and why it's prescribed for hypothyroidism. Hypothyroidism is a condition wherein the thyroid gland fails to produce enough thyroid hormones, which play a crucial role in regulating the body's metabolism. Thyroid hormone deficiency can cause a wide range of symptoms, such as fatigue, cold intolerance, weight gain, and anxiety, among others. The most common cause of hypothyroidism is Hashimoto's thyroiditis, an autoimmune disorder where the immune system attacks the thyroid.

Levothyroxine, also known by its brand names Synthroid, Levoxyl, and Tirosint, is a synthetic thyroid hormone that is chemically identical to the naturally occurring hormone thyroxine (T4). It's a prescription drug that works by replacing or supplementing the insufficient thyroid hormone levels in people with hypothyroidism, helping them maintain healthy metabolism and overall well-being.

What is diarrhea?

According to WHO, Diarrhea is when your stools are watery and loose and occur more frequently than normal. Infections, medications, allergic reactions, and digestive disorders can cause it.

Common symptoms of diarrhea include:

  • Loose, watery stools that occur more frequently than usual

  • Abdominal cramps or pain

  • Nausea and vomiting

  • Bloating and gas

  • Dehydration, which can cause dry mouth, thirst, fatigue, dizziness, and dark urine.

Can levothyroxine lead to diarrhea?

Now that we have a basic understanding of levothyroxine and its role in hypothyroidism treatment, let's address the main question: does levothyroxine cause diarrhea? While the thyroid medication levothyroxine is generally well-tolerated, diarrhea is indeed a potential side effect. A study found that up to 25% of patients with hyperthyroidism have mild-to-moderate diarrhea side effects with frequent bowel movements.

However, it is important to note that diarrhea is not universally experienced by levothyroxine users, and its occurrence may depend on individual factors such as dosages, co-existing medical conditions, and individual sensitivities.

Why does levothyroxine cause diarrhea? 

There are several reasons why levothyroxine may cause diarrhea in some individuals. 

1. Overstimulation

Diarrhea could be a result of an overstimulation of the gastrointestinal tract due to an excessive dose of levothyroxine. This is because thyroid hormones act on almost all organs within the gastrointestinal tract. In essence, when the body receives more thyroid hormone than it requires, it may speed up various bodily processes, including digestion, resulting in diarrhea. This is also why people with hyperthyroidism (an overactive thyroid) often experience diarrhea as a symptom.

2. Malabsorption

Another possible reason for diarrhea is the malabsorption of the medication. Levothyroxine absorption can be affected by various factors, such as food and other medications. If your body doesn't absorb levothyroxine properly, it may lead to an imbalance in the gut, resulting in diarrhea.

3. Lactose intolerance

Some levothyroxine formulations contain lactose, which could cause diarrhea among those who are lactose intolerant. If you suspect that lactose intolerance could be the reason for your diarrhea, consult your doctor about a lactose-free levothyroxine option.

4. Individual sensitivity

You may simply be more sensitive to levothyroxine or its inactive ingredients, causing your gastrointestinal systems to react negatively and lead to diarrhea. For example, people who have autoimmune thyroid disease and celiac disease may not be able to take medications that contain gluten. Some brands of levothyroxine are not gluten-free. Therefore, be sure to check the ingredient list before you take anything.

5. Adjustment period

When starting levothyroxine or adjusting the dosage, the body may need some time to adapt to the new hormone levels. During this adjustment period, you may experience diarrhea as your body tries to find the right balance of thyroid hormones. This side effect is usually temporary and should resolve as your body gets used to the medication.

6. Changes in gut microbiota

The gut microbiota, or the community of microorganisms living in the human digestive tract, plays a crucial role in maintaining gut health and preventing diarrhea. Levothyroxine has been shown to influence gut microbiota composition, which could potentially contribute to diarrhea in some people. However, more research is needed to fully understand the impact of levothyroxine and thyroid hormones on gut microbiota and its link to diarrhea.

7. Pre-existing gastrointestinal conditions

If you have pre-existing gastrointestinal conditions, such as irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD), you may be more prone to experiencing diarrhea while on levothyroxine. The introduction of thyroid hormone replacement therapy may exacerbate underlying gastrointestinal issues, resulting in an increased incidence of diarrhea.

8. Inability to Convert T4 to T3

Levothyroxine is a synthetic T4 hormone, and for it to be effective, the body needs to convert it to the active T3 hormone. However, some people may have difficulty converting T4 to T3 due to genetic factors, nutritional deficiencies, or other health issues. If your body is unable to efficiently convert T4 to T3, levothyroxine may not be the right treatment for you, and the imbalance of thyroid hormones could contribute to diarrhea.

If you suspect that your body is not converting T4 to T3 effectively, it's essential to discuss this with your healthcare provider. They may recommend additional testing, such as measuring thyroid stimulating hormone (TSH), as well as both free T3 and free T4 levels. The thyroid blood test results can help them assess your thyroid function more accurately.

In some cases, your doctor might consider prescribing a combination therapy of synthetic T4 (levothyroxine) and synthetic T3 (liothyronine) like Cytomel or utilizing a natural desiccated thyroid (NDT) medication like Armour Thyroid and NP Thyroid, which contains both T4 and T3 derived from animal sources. You can also buy desiccated thyroid online in the form of a supplement, such as VitaliThy. This alternative treatment approach may help alleviate diarrhea and other symptoms associated with an inability to convert T4 to T3.

How to manage and prevent diarrhea due to levothyroxine?

If you experience diarrhea while taking levothyroxine, there are several strategies to help manage and prevent this side effect.

1. Monitor your dosage

As mentioned earlier, an excessive dose of levothyroxine can cause diarrhea. It is crucial to work closely with your doctor to find the appropriate dosage for your needs.

2. Gradual dose increase

If you are starting levothyroxine or adjusting your dosage, a gradual increase may minimize the risk of diarrhea. Your doctor may recommend increasing the dose slowly over several weeks, allowing your body to adjust to the new levels of thyroid hormone.

3. Take levothyroxine on an empty stomach

To ensure optimal absorption, take levothyroxine on an empty stomach at least 30 minutes to one hour before eating your first meal of the day. Avoid taking it with food or beverages that can interfere with its absorption, such as coffee, tea, and calcium-rich dairy products.

4. Be mindful of drug interactions

Some medications and supplements can interfere with the absorption of levothyroxine, which may contribute to diarrhea. Discuss any medications or supplements you take with your doctor to ensure they do not hinder levothyroxine's effectiveness.

5. Avoid lactose-containing formulations

If you believe that lactose intolerance may be the culprit behind your diarrhea while taking levothyroxine, consult with your doctor about the possibility of trying a lactose-free alternative.

WP Thyroid, a natural and hypoallergenic NDT medication, used to be an excellent choice as it was free from lactose, gluten, and artificial colorings. However, due to its unavailability, you may consider the NDT supplement VitaliThy as a suitable alternative. VitaliThy, a natural desiccated thyroid you can buy online, is not only lactose-free but also devoid of gluten, fish, shellfish, eggs, artificial flavorings, and colorings. As a result, VitaliThy can be a safe option for those with food sensitivities or allergies.

6. Stay hydrated

If you do experience diarrhea, it is crucial to stay hydrated by drinking plenty of fluids, such as water, clear broth, or oral rehydration solutions. This is because diarrhea can cause your body to lose a significant amount of water and electrolytes, leading to dehydration. When you're dehydrated, your body doesn't have enough fluids to function correctly, which can cause a range of health problems.

7. Change your diet

Some people may find that specific dietary changes, such as eating smaller, more frequent meals or temporarily avoiding high-fiber foods, can help alleviate diarrhea associated with levothyroxine treatment. Aside from providing relief from diarrhea, changing your diet may also help you with weight loss.

8. Manage stress

As stress can exacerbate gastrointestinal issues, learning to cope with stress effectively through relaxation techniques, exercise, or engaging in hobbies can help manage diarrhea. Hypothyroid patients may also find the ease of symptoms by managing their stress.

9. Over-the-counter medication for short-term relief

For temporary relief from diarrhea, over-the-counter medications like loperamide (Imodium) may be considered. However, it's crucial to consult with your healthcare provider before using these medications to ensure they are appropriate for your situation and don't mask or exacerbate any underlying issues.

10. Consider switching to natural desiccated thyroid (NDT)

If you continue to experience diarrhea while taking levothyroxine, you may discuss with your doctor the possibility of switching to an NDT alternative. NDT medications, such as Armour Thyroid and Nature-Throid, as well as NDT supplements like VitaliThy, contain a combination of T4 and T3 hormones and may be better tolerated by some individuals.

Other causes of diarrhea to watch out for

Sometimes, it might not be levothyroxine or hypothyroidism that's causing your diarrhea. Here are some of the causes of diarrhea:

  • Viral infections: The most common cause of diarrhea is a viral infection, such as norovirus, rotavirus, or adenovirus.

  • Bacterial infections: Salmonella, E. coli, and Campylobacter can cause diarrhea.

  • Parasites: Parasites such as Giardia lamblia, Cryptosporidium, and Entamoeba histolytica can cause diarrhea.

  • Medications: Sometimes, antibiotics, antacids, and chemotherapy drugs can cause diarrhea as a side effect.

  • Digestive disorders: Such as inflammatory bowel disease, irritable bowel syndrome, celiac disease, and lactose intolerance, can cause diarrhea.

  • Allergic reactions: When a person has an allergic reaction, their immune system overreacts to a substance (called an allergen) that it perceives as a threat. This immune response can trigger inflammation throughout your body, including in the digestive system, leading to symptoms such as diarrhea.

  • Stress and anxiety: Emotional stress and anxiety can affect your entire body and cause diarrhea.

  • Hormonal imbalances: While hormonal imbalances can affect your entire body, they are not typically a direct cause of diarrhea. It indirectly contributes to diarrhea by causing changes in the gut microbiome or digestive processes.

Other factors that can cause diarrhea include radiation therapy, alcohol abuse, and certain medical conditions such as hyperthyroidism and diabetes.

Conclusion: Diarrhea is a potential side effect of levothyroxine

While diarrhea can be a potential side effect of levothyroxine, it is not a universal experience for all users. By understanding the possible causes and taking proactive steps to manage and prevent diarrhea, you can find the best possible treatment for your hypothyroidism without the discomfort of unwanted gastrointestinal side effects.

If you continue to experience diarrhea while taking levothyroxine due to lactose intolerance, celiac disease, or an inability to effectively convert T4 to T3, you may consider exploring VitaliThy as an alternative option. VitaliThy, a natural desiccated thyroid you can buy online, is free from common allergens and provides both T4 and T3 thyroid hormones. As a result, VitaliThy may prove to be a more suitable and effective solution for those who are unable to find relief with levothyroxine.

Wojciech Majda
Wojciech Majda

Leave a comment

Comments will be approved before showing up.

Also in Natural Desiccated Thyroid blog

What are my chances of getting pregnant with hypothyroidism?
What are my chances of getting pregnant with hypothyroidism?

July 17, 2023 13 min read

When it comes to getting pregnant, it's not just about the birds and the bees. There are actually a whole host of medical factors at play. One such factor is your thyroid function. It's time to shed light on an essential question: "How can hypothyroidism influence my chances of becoming pregnant?"
PCOS and hypothyroidism: what's the connection?
PCOS and hypothyroidism: what's the connection?

July 17, 2023 11 min read

How to boost metabolism with hypothyroidism: Metabolic thyroid supplement, exercises, and more
How to boost metabolism with hypothyroidism: Metabolic thyroid supplement, exercises, and more

July 17, 2023 9 min read

Hypothyroidism can be a challenging condition for everyone, but there are some simple steps you can take to boost your health! From metabolic thyroid supplements to exercises, this article will show you how to get your metabolism up and running again.

Sign up for our Newsletter