Our Products
About Us
Contact Us
Hello Sign In
Your Account
My Cart

Synthroid Side Effects

Pin it
Synthroid is a prescription drug designed to treat hypothyroidism, and it can cause several side effects to the body.

Synthroid or Levothyroxine sodium is a prescription medication that is designed to treat hypothyroidism and help manage the symptoms that are associated with the condition. 

Synthroid’s active ingredient is called levothyroxine sodium, a synthetic hormone that is identical to thyroxine or T4 – one of the two hormones produced by the thyroid gland.

How Does Synthroid Work?

thyroid glandTo understand how Synthroid works, it is essential to first understand how the thyroid gland works and what happens during hypothyroidism.

Essentially, the thyroid gland produces two specific hormones – levothyroxine or t4 and triiodothyronine or t3. these two hormones act on almost all the cells in the body, regulating the body’s metabolism. in cases of hypothyroidism though, the thyroid gland does not produce enough t4 or t3, which leads to hormonal imbalance, causing a host of unwanted symptoms. 

Initially, Synthroid is taken to supplement the lack of T4; but because the body easily synthesizes T4 into T3, it is also successfully used to improve low levels of both T3 and T4 hormones.

What Are The Side Effects of Synthroid?

Like other prescription medications, Synthroid may produce unwanted side effects on the body.

Most of the time, the side effects are due to under-replacement or over-replacement, which is caused by under-use or over-use of the product.

Individuals who do not get enough levothyroxine may continue to experience the symptoms of hypothyroidism. Likewise, hyperthyroidism may also occur if one gets too much of the synthetic hormone.

CHEST PAINHere are some of the symptoms that are associated with overtreatment:

  • Rapid heartbeat or palpitations
  • Chest pain
  • Shortness of breath
  • Muscle weakness
  • Nervousness and anxiety
  • Irritability
  • Sleeplessness
  • Tremors
  • Nausea and vomiting
  • Frequent bowel movements
  • Weight loss
  • Excessive sweating
  • Fever
  • Seizures
  • Strokes
  • Coma
  • Death

partial hair lossAside from these symptoms, which are associated with over-treatment, hair loss is often noted among users. Partial hair loss does not just occur during over-treatment but also occurs in patients who take just the right amount of medication.

Partial hair loss is temporary and hair usually grows back after several months.

Allergic reaction to the drug is rare, but it can happen. Allergic reactions to look out for include:

Allergic Reactions to Synthroid


Swelling of the mouth and throat area

In case of these symptoms, medical attention should be acquired immediately.

While some side effects are not as severe as others, it is important to keep track of these symptoms and notify the doctor right away to make sure that the side effects are immediately attended to. Some doctors recommend the use of a treatment tracker which patients can use to track when they took the medication and list down details related to unwanted symptoms and side effects.

Drug Warnings and Precautions

If you have hypothyroidism and are recommended by your doctor or healthcare provider to take Synthroid, you must inform him or her if you have the following conditions:

Conditions to Consider:
Adrenal disorder


Heart disease or a recent heart attack
Pregnancy or lactation

Lastly, here are some things to remember about Synthroid:

  • Synthroid should only be used upon the recommendation of a health care provider and should not be used by individuals who do not have thyroid problems. Likewise, it should not be used to induce weight loss since doing so can cause life-threatening problems. 
  • Synthroid should be taken in regular doses as tiny changes in the dosage can render the drug ineffective or can cause over-stimulation of the thyroid gland. 
  • Blood tests should be done regularly to ensure that treatment is stable and the thyroid hormone levels are also stable, too. 
  • The medication can aggravate heart conditions. Most individuals with heart problems usually start with a low dosage.
  • The medication can also increase the risk of osteoporosis, especially if the doses are too high. Regular check-ups and tests are recommended so that the healthcare provider can recommend just the right dose to improve thyroid hormone levels.
  • It may take several weeks before the medication starts working. Do not increase your dose without your healthcare provider’s consent.
  • Synthroid can pass through a woman’s breast milk, but it is unlikely to cause harm to her baby.

Because Synthroid is a prescription drug, side effects are always a risk. thus, proper precautions must be taken to ensure the safe administration of the drug. Likewise, it is important to pay close attention to any changes in the body or possible side effects to make sure that the doctor can check it out as soon as possible.

Next Article: Thyroid Health | How to Boost T3 and T4 Levels