What Happens If I Stop Taking Levothyroxine for Hashimoto's?

October 6, 2025 •

4 min read

Affecting about 5 in 100 people in the United States, Hashimoto's disease is the nation's most common cause of hypothyroidism [1.7.3, 1.7.5]. For many, this raises the question: what happens if I stop taking levothyroxine for Hashimoto's, the primary treatment for the condition? [1.5.2, 1.5.6]

Quick Summary

Stopping levothyroxine for Hashimoto's causes a gradual return of hypothyroid symptoms like fatigue, weight gain, and depression as the body's hormone levels drop [1.2.1]. This can lead to severe long-term complications, including heart problems and a rare, life-threatening condition called myxedema coma [1.5.4, 1.8.2].

Key Points

Symptom Return: Stopping levothyroxine causes a gradual return of hypothyroid symptoms like fatigue, weight gain, and brain fog within weeks [1.2.1, 1.4.1].
Long Half-Life: Levothyroxine has a half-life of 6-7 days, meaning it takes over a month to fully clear from your system [1.2.3, 1.4.5].
Heart Health Risks: Untreated hypothyroidism from stopping medication increases the risk of high cholesterol, heart disease, and heart failure [1.8.3, 1.8.4].
Myxedema Coma: In rare cases, severe, untreated hypothyroidism can lead to myxedema coma, a life-threatening medical emergency [1.5.6, 1.6.2].
Medical Supervision is Crucial: Never stop or change your levothyroxine dose without consulting a doctor, who can safely manage your treatment [1.5.4].

Understanding Hashimoto's and the Role of Levothyroxine

Hashimoto's disease is an autoimmune disorder where the immune system mistakenly attacks the thyroid gland [1.8.1]. This chronic inflammation can damage the thyroid, reducing its ability to produce essential thyroid hormones [1.7.1]. These hormones regulate many of the body's critical functions, including metabolism, heart rate, and body temperature [1.5.6]. When production falls, it leads to hypothyroidism, or an underactive thyroid [1.2.1].

Levothyroxine is a synthetic form of the T4 hormone (thyroxine) that the thyroid gland produces naturally [1.5.6]. It serves as a hormone replacement therapy, supplementing what the damaged thyroid can no longer make [1.5.1]. For most individuals with Hashimoto's, levothyroxine is a lifelong medication necessary to manage symptoms and prevent long-term health consequences [1.5.2].

The Immediate Aftermath: What Happens When You Stop?

Because levothyroxine has a long half-life of about six to seven days, the effects of stopping the medication are not instantaneous [1.2.3]. It can take four to six weeks for the drug to be completely eliminated from the body [1.4.5]. However, symptoms of hypothyroidism typically begin to return within the first few weeks as hormone levels decline [1.4.1].

Symptom Timeline After Stopping Levothyroxine

Week 1: Initial changes may be subtle. Some individuals might experience mild fatigue, difficulty concentrating, or a dip in mood, while others may not notice significant changes yet [1.4.1].
Week 2: Symptoms begin to intensify. As T4 levels decrease, fatigue, intolerance to cold, and weight gain become more apparent as the body's metabolism slows down [1.4.1].
Week 3: Cognitive functions may decline further, leading to brain fog, forgetfulness, and mood swings. Physical symptoms like dry skin, muscle weakness, and hair loss may also start to appear [1.4.1, 1.5.6].
Week 4 and Beyond: The metabolic slowdown continues, potentially leading to more weight gain. Joint pain and depression can worsen [1.4.1]. If discontinuation continues, symptoms will become progressively more severe, significantly impacting quality of life [1.4.1].

Short-Term and Long-Term Health Risks

Abruptly stopping levothyroxine without medical supervision goes beyond the discomfort of returning symptoms; it poses significant health risks.

Re-emergence of Hypothyroid Symptoms

Once the medication is out of your system, the full spectrum of hypothyroid symptoms will return. These include:

Severe fatigue and sluggishness [1.8.4]
Unexplained weight gain [1.2.1]
Depression and memory problems [1.3.2]
Constipation [1.2.2]
Dry skin and hair loss [1.2.1]
Muscle weakness, aches, and joint pain [1.3.2]
Increased sensitivity to cold [1.8.4]
Irregular or heavy menstrual periods in women [1.2.1]

Serious Long-Term Complications

Untreated hypothyroidism resulting from stopping medication can lead to severe, systemic health problems:

Heart Problems: Low thyroid hormone levels can lead to high LDL ("bad") cholesterol, increasing the risk of heart disease and heart failure [1.8.3, 1.8.4]. It can also cause a slowed heart rate and an enlarged heart [1.8.2].
Infertility and Pregnancy Complications: Untreated hypothyroidism can cause reduced libido, irregular ovulation in women, and lowered sperm count in men [1.8.4]. During pregnancy, it increases the risk of miscarriage, preterm birth, and developmental problems in the baby [1.8.4].
Goiter: The pituitary gland may release more thyroid-stimulating hormone (TSH) to try and force the damaged thyroid to produce more hormones. This overstimulation can cause the thyroid gland to enlarge, a condition known as a goiter, which can interfere with swallowing or breathing [1.8.4].
Myxedema Coma: This is the most severe consequence of untreated hypothyroidism. It is a rare, life-threatening condition where the body's functions slow down to a critical point, leading to profound lethargy, confusion, low body temperature, and eventually coma [1.6.2, 1.8.2]. Myxedema coma is a medical emergency that requires immediate treatment in an intensive care unit [1.2.1]. The fatality rate can be as high as 60% without treatment [1.5.6].

Comparison: On Levothyroxine vs. Off Levothyroxine


Feature	Medically Managed on Levothyroxine	Stopped Levothyroxine (Untreated)
Energy Levels	Normal energy, ability to exercise [1.8.1]	Severe fatigue, sluggishness, inability to handle exercise [1.4.1, 1.5.5]
Metabolism & Weight	Stable weight [1.5.6]	Slowed metabolism, unexplained weight gain [1.2.1]
Mental State	Clear thinking, stable mood [1.5.6]	Brain fog, memory problems, depression, mood swings [1.4.1, 1.8.4]
Heart Health	Normal heart rate, managed cholesterol levels [1.8.1]	Slowed heart rate, high cholesterol, increased risk of heart disease [1.8.3, 1.8.4]
Physical Comfort	Normal body temperature regulation [1.5.6]	High sensitivity to cold, joint and muscle pain [1.4.1]
Severe Risk	Low risk of complications with proper dosage	Risk of goiter, heart failure, and life-threatening myxedema coma [1.8.2, 1.8.3]

Never Stop Medication Without a Doctor's Guidance

While some people may feel better temporarily after stopping levothyroxine—perhaps due to an incorrect dosage that was causing symptoms of an overactive thyroid—these effects are short-lived [1.5.6]. The underlying hypothyroidism will always re-emerge.

Under no circumstances should you stop taking levothyroxine or adjust your dose without consulting your healthcare provider. A doctor can order blood tests to check your TSH levels and determine if a dosage adjustment is needed [1.5.3]. If you are experiencing side effects, your doctor can work with you to find a solution, which might involve changing your dose, not stopping the medication altogether [1.5.4].

Conclusion

For individuals with Hashimoto's disease, levothyroxine is a critical, often lifelong, treatment. Stopping this medication is not a passive act; it actively allows hypothyroidism to return, bringing with it a cascade of symptoms that degrade quality of life. More dangerously, it exposes you to severe long-term health risks, including cardiovascular disease, infertility, and the potentially fatal myxedema coma [1.5.4, 1.8.2]. The decision to stop or alter your thyroid medication is a serious one that should only ever be made in close consultation with a healthcare professional.

For more information from a leading authority on thyroid conditions, you can visit the American Thyroid Association.

Frequently Asked Questions

While it takes 4 to 6 weeks for levothyroxine to completely leave your system, you may start to experience returning symptoms of hypothyroidism, like fatigue, within the first one to two weeks [1.4.1, 1.4.5].

In rare but severe cases, abruptly stopping levothyroxine can lead to a life-threatening condition called myxedema coma, which can be fatal if not treated immediately [1.2.1, 1.5.6]. This is the most serious risk associated with untreated hypothyroidism.

No, you are more likely to gain weight if you stop taking levothyroxine. The medication supports your metabolism, and stopping it will cause your metabolism to slow down, leading to weight gain [1.2.1, 1.5.6].

Missing a single dose of levothyroxine is generally not a cause for concern and is unlikely to cause symptoms due to the medication's long half-life. If you remember, take the missed dose as soon as you can, unless it's almost time for your next one [1.2.1, 1.5.6].

A doctor might recommend stopping or lowering the dose if your thyroid function recovers (in rare cases of temporary hypothyroidism), or if your TSH levels indicate your dose is too high, causing symptoms of hyperthyroidism. This should only be done under strict medical supervision with regular blood tests [1.2.2].

There is no cure for Hashimoto's disease itself, as it is a chronic autoimmune condition [1.2.1]. However, the resulting hypothyroidism is highly manageable with lifelong thyroid hormone replacement therapy like levothyroxine [1.8.1].

Myxedema coma is a rare, life-threatening complication of severe, long-term, untreated hypothyroidism [1.8.4]. Its symptoms include a significant drop in body temperature, slowed breathing, confusion, lethargy, and unconsciousness, and it requires immediate emergency medical treatment [1.6.2, 1.6.3].