Levothyroxine is the generic name of a drug prescribed in the treatment of hypothyroidism, goiters and thyroid cancer. It is sold under such brand names as Unithroid, Levothroid, Synthroid and Levoxyl. Hypothyroidism sufferers have a condition in which a gland called the thyroid fails to produce the correct amount of the thyroid hormone. Levothyroxine is administered as a pill.
Serious Side Effects
Serious side effects produced by levothyroxine may need medical treatment, so call your doctor immediately if you get any of them 2. Less common serious side effects, states the Mayo Clinic, may include:
- diplopia or double vision
- a retardation of child growth
- appetite changes
- discomfort or pain in the chest
- breathing that is irregular
- bone mineral density decreases
- joint inflammation
- lowered output of urine
- pulse increases
- welts or hives
Others may include
- breathing problems
- bodily motion problems
- stiffness or pain in the muscles
- swallowing difficulties
- abnormal liver function
- dilated neck veins
- menstrual cycle changes
- eye pain
- extreme fatigue
- swollen patches on the genitals
- in the throat
- on the tongue or hands or on the face
Rarely, some people taking levothyroxine have had seizures.
Temporary Side Effects
Midol Side Effects
Levothyroxine can induce some side effects at the beginning of treatment that will go away as you acclimate to it 2. These are categorized as less common temporary side effects and include:
- abnormal weakness or tiredness
- abdomen cramps
- changing emotional moods
- fertility problems
- excessive sweating
- hair loss
- skin redness
- sensation of bodily warmth
- appetite increases
- muscle weakness
If any of these persist call your physician.
Overdose Side Effects
Go to the nearest emergency room if you take more than the prescribed dose of levothyroxine.
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- Mayo Clinc website: Levothyroxine
- Drugs.com website: Levothyroxine Side Effects
- GoodRx. Why Synthroid is the most prescribed drug in the U.S. Updated November 7, 2017.
- Fallahi P, Ferrari S, Ruffilli I, Bonatti A, Paparo S, Materazzi G, et al. Oral L-Thyroxine in gel capsule versus the tablet formulation in patients submitted to total thyroidectomy: Preliminary data. Thyroid. 2017;27(S1):A166–A188. doi:10.1089/thy.2017.29046.abstracts.
- Jonklaas J, Bianco AC, Bauer AJ, et al. Guidelines for the treatment of hypothyroidism: Prepared by the American Thyroid Association Task Force on thyroid hormone replacement. Thyroid. 2014;24(12):1670–751. doi:10.1089%2Fthy.2014.0028.
- London S. Generic, brand-name levothyroxine have similar cardiovascular cutcomes. Clinical Endocrinology News. MDedge. Updated October 29, 2017.
- GoodRx. Levothyroxine.
- U.S. Food and Drug Administration (FDA). U.S. Department of Health and Human Services. Levothyroxine sodium product information. Updated November 18, 2019.
- Tirosint.com. Tirosint (levothyroxine sodium) capsules.
- 87th annual meeting of the American Thyroid Association. Thyroid. Vol. 27, No. S1. Updated October 1, 2017.
- Tirosint. What makes Tirosint different?
Carole Anne Tomlinson is a registered nurse with experience in rehabilitation, nutrition, chemical dependency, diabetes and health problems related to the elderly. Tomlinson holds a Bachelor of Arts in criminal justice and is presently working on her master's degree in nursing. Her screenplays have been viewed by Merchant Ivory, Angela Lansbury and Steven King's associates.