What Are The Common Side Effects Of Levothyroxine?

Drugs January 23rd, 2023

Levothyroxine is approved by the US Food and Drug Administration “FDA” to treat a common condition known as hypothyroidism. According to recent statistics, five per cent of the US population has an underactive thyroid gland. Another less common use is obesity when the Body Mass Index “BMI” is 30 or higher. When treating obesity, Levothyroxine must not be combined with other weight loss supplements or prescription drugs. But what are best use cases and Side Effects Of Levothyroxine, let us get into the detail.

How Long Does It Take For Levothyroxine To Work?

Levothyroxine side effects

As of 2019, nearly 20 million patients were taking Levothyroxine daily. Unlike some medications, Levothyroxine begins working almost immediately after the initial dose. With this said, patients are advised to not expect immediate changes in how they feel. For example, hypothyroidism symptoms range from muscle aches, tiredness, and feeling blue. While the first dose of Levothyroxine may start replacing your thyroid hormone, it can take up to three weeks for the symptoms to subside.

Primary care physicians schedule new Levothyroxine patients for a follow-up blood test during the initial visit. Patients can expect a follow-up TSH test, which entails a laboratory technician taking a blood sample. The results are rarely readily available in outpatient settings. The physician will make dosage adjustments upon receiving the results in two to three days.

What Are The Most Common Side Effects Of Levothyroxine?

All prescription medications, including Levothyroxine, have side effects, ranging from mild to severe. New patients are advised to speak with their primary care physician and/or pharmacist about potential side effects. Be aware, severe side effects pose serious health risks for patients of all ages. Knowing the side effects in advance could save your life in life-threatening situations.

Minor side effects are to be expected in all patients. Some patients have reported no side effects for several months. Every patient responds to Levothyroxine in a unique manner.

  • Weight Gain – Levothyroxine patients oftentimes report weight gain after several months of the initial dose. This is nothing to be alarmed about because Levothyroxine increases thyroid hormone levels as well as cortisol levels. Cortisol is a hormone produced by the adrenal glands (endocrine glands). High cortisol levels increase food cravings, especially fatty, sweet, and salty food.
  • Diarrhea – Levothyroxine patients can expect to have bouts of diarrhea almost immediately after the first few weeks. The digestive system is prompted to produce more digestive juices as the thyroid hormone levels increase. If diarrhea becomes persistent, patients should consult with their primary care physician for an over-the-counter antimotility or probiotic medicine.
  • Appetite Changes – Levothyroxine has been linked to changes in appetite, especially in new patients. The culprit is obviously the medicine that regulates the metabolism. An increase in appetite has also been reported in many patients.
  • Fever – Levothyroxine can cause a low-grade fever but only in rare cases.
  • Hair Loss – Levothyroxine can cause hair loss for several months following the initial dose. Once the TSH level is regulated, the hair will stop following out and new hair growth should be noted. If hair loss becomes persistent, patients should consult with their primary care physician. A dermatologist visit may be required for another underlying condition.
  • Menstrual Cycle Changes – Levothyroxine can alter a female patient’s menstrual cycle. Any changes in thyroid function impact menstruation. Symptoms can range from mild to heavy periods or irregular periods. Some female patients have reported missed periods when taking Levothyroxine. It can take up to six months to see improvement in mild cases.

Common Levothyroxine Uses

Levothyroxine is a common medication primarily given to individuals with hypothyroidism which means they have an underactive thyroid gland. The gland is responsible for producing thyroid hormones that help manage growth and energy levels. Individuals with hypothyroidism are unable to produce enough hormones so they often feel lethargic and may experience stunted growth.

Levothyroxine side effects

Using Levothyroxine can help offset this issue by supplementing the thyroxine that is not being produced naturally by the thyroid. Individuals with hypothyroidism will need to visit a medical professional for diagnosis and to receive a prescription.

Levothyroxine can only be obtained with a prescription. Besides being used to treat hypothyroidism, the medication is also approved for the treatment of thyroid-stimulating hormone suppression. As a result, it can also assist in the treatment of thyroid cancer and certain goiters.

Levothyroxine Doses

It can be difficult to find the perfect dose for each patient. Therefore, it is essential for patients to work with medical professionals to get the safest and most effective dose. Typically, the patient’s dose will start at a minimum point and increase over several weeks. Certain patients may be required to start with an even lower dose due to their age or preexisting health conditions.

It is common for adults to begin taking as few as 50 micrograms daily. Others will start at 100 micrograms each day. Over several weeks, the dose will be gradually increased until the patient is consuming up to 200 micrograms daily. The average dose required to return TSH levels to normal is between 100 and 125 mcg.

Usually, the dose is determined by providing 1.6 micrograms per kilogram of body weight. There are several unique situations that will require more precise calculations. For instance, the doctor will need to determine the exact dose for children under 12 based on their weight.

Patients over 50 and those with heart disease are usually asked to consume a lower dose of Levothyroxine initially. To avoid under or overdosing, work with a licensed doctor and always follow their guidelines.

Levothyroxine Alternatives

Certain patients should not take Levothyroxine since it can lead to complications. Instead, the preferred medical professional may recommend a suitable alternative. While there are others, some alternatives include Levoxyl, Thyrolar, Cytomel, and Synthroid.

It is best for patients to discuss their options with a licensed professional to avoid allergic reactions and further complications.

  • Armour Thyroid – Armour Thyroid and Levothyroxine are often compared because they’re prescribed for the same purposes. In one double-blind study, participants taking Armour Thyroid lost more weight than those using Levothyroxine. Patients also reported feeling better when using Armour Thyroid, but it may not be right for everyone.
  • Levoxyl – Levoxyl may be a good alternative to the Levothyroxine the patient is taking. Just remember that Levoxyl actually contains Levothyroxine which is the medication’s active ingredient. The primary difference is that Levoxyl contains unique inactive ingredients that can lead to different results for each user.
  • Synthroid – Synthroid is another common replacement medication, but its active ingredient is Levothyroxine. Patients needing to avoid this ingredient will have to search for a different thyroid medication. It is never a good idea to switch too frequently because doing so can lead to abnormal results on thyroid function tests.
  • Thyrolar – While Thyrolar was once a good replacement, the brand is no longer available since it was discontinued. Regardless, it helped patients dealing with symptoms related to low thyroid hormone levels, including weight gain, goiter, and tiredness.
  • Cytomel – Cytomel and Levothyroxine are similar since they contain synthetic thyroid hormone ingredients. However, the main difference is the version included. Cytomel or Liothyronine contains the T3 hormone whereas Levothyroxine contains the T4 hormone. Unfortunately, Cytomel is absorbed faster so it possesses a higher risk of adverse effects and toxicity.

Again, patients should always discuss their options with a licensed medical professional. Even though some of these medications contain Levothyroxine, the inactive ingredients may differ from one medication to the next. Working with a licensed doctor ensures that the patient gets the right medication that can provide the best and safest results.

Potential Levothyroxine Interactions

While Levothyroxine is generally very safe, it can cause certain side effects. The medication can also interact with other substances so caution is advised. For instance, Levothyroxine can have significant interactions with iron supplements, antacids, calcium, ion exchange resins, and bile acid sequestrants. Individuals taking Levothyroxine should wait at least four hours after consuming this medication before using any of the aforementioned drugs.

Certain medications can reduce the body’s ability to absorb Levothyroxine so they should not be taken simultaneously. For instance, iron salts, sucralfate, calcium salts, and antacids should be taken much later. Other medications that should not be used with Levothyroxine include Rifampin, proton pump inhibitors, and phenobarbital.

As for Vitamin C, some research suggests this vitamin can improve the body’s ability to absorb levothyroxine, but there is no concrete proof. It is best to speak to a healthcare provider before using vitamin C and levothyroxine.

Furthermore, levothyroxine should not be mixed with coffee, grapefruit, or alcohol since these substances can impact thyroid hormone levels.

Levothyroxine Price Discounts

The average retail price of Levothyroxine is nearly $13 making it an expensive medication for daily users. Thankfully, those prescribed this medication can save by taking advantage of the CharityRx prescription discount card.

It is also covered by most insurance plans as well as Medicare. Patients should explore their options before paying full price for Levothyroxine and other prescription medications.


Levothyroxine is a commonly prescribed medication primarily used for patients with underactive thyroid glands. In the United States, it is estimated that roughly 1 in 20 Americans 12 years and older have hypothyroidism. The majority of these individuals have autoimmune thyroiditis meaning their immune systems end up attacking their thyroid glands. Side Effects Of Levothyroxine will be less while you take this with medical experts advice.

Taking a thyroid replacement is an effective way to minimize the symptoms and enjoy a long, fulfilling life. Many patients use levothyroxine since it is one of the most reliable thyroid replacements. Individuals using this medication should stay away from coffee, alcohol, antacids, grapefruit, and other substances that could impact their thyroid hormone levels.

CharityRx pharmacy discount card

You can download the CharityRx discount card and get up to 80% discount on medicines at any of the partner pharmacies closest to you. The discount may vary depending on the drug and location.