Synthroid Side Effects, Upsides, Downsides & Tips

Synthroid is the brand name for Levothyroxine. This medication is used in the treatment of hypothyroidism which is an underactive thyroid. Synthroid produces thyroid hormones when the thyroid gland fails to produce them naturally. Lack of thyroid hormones can occur naturally or as a result of an injury to the thyroid gland.


This medicine performs an essential function as, without sufficient levels of thyroid in the body, the human body will not be able to function properly. Low thyroid levels result in deteriorated mental and physical abilities, especially in children.

Synthroid is also prescribed to treat various thyroid disorders, for example, thyroid cancer.


Side Effects

Your doctor will prescribe this medicine to you if the benefits are far greater than the side effects that you may experience. Also, usually these side effects go away over time as your body becomes adjusted to the medicine. Some commonly experienced adverse effects of this medicine are:

  • Trouble getting pregnant
  • High blood pressure levels
  • Weight loss
  • Low levels of calcium in the blood

Apart from this, people may also experience some other side effects. Although these are not as common, if you experience these adverse effects, you should contact your doctor immediately. These rare side effects vary in intensity and include the following:

  • Angina
  • Hives
  • Fast heart rate
  • Abnormal heart rate
  • Heart attack
  • Going into heart failure
  • Rash
  • Seizures
  • Difficulty breathing


  • Mood swings
  • Diarrhea
  • Hair loss
  • A headache
  • Feeling hungry
  • Muscle cramps
  • Irregular menstrual cycle
  • Nervousness
  • Low levels of energy



How to Use

Synthroid is to be taken once every day with a glass of water. This medicine should be taken at least 1 hour prior to eating your breakfast. It is recommended that you swallow the Synthroid capsule without breaking, crushing or chewing it.

However, people who find it difficult to swallow a whole capsule should opt for Synthroid tablets.

Crush the tablet and mix it in with 2 tablespoons of water (approximately 10 milliliters). When giving it to children, use a spoon or dropper. Do not prepare the dosage beforehand. Also, for infants, do not mix Synthroid in their formula.


Ensure that you do not stop taking this medicine on your own as the dosage and schedule of the drug is different for each individual and depends upon their age, weight, and condition.

Some medicines, like iron, calcium supplements, and others should not be taken with Synthroid. Have a gap of at least 4 hours between Synthroid and these medicines.




  • Inform your doctor if you are allergic to any or to all the ingredients of Synthroid. Tell your doctor of any other (major and minor) allergies that you suffer from.
  • Inform your doctor if you suffer from any type of heart disease, thyroid problem, diabetes or high blood pressure levels.
  • Tell your doctor and surgeon of all the medicines that you are taking, be they prescription, non-prescription or herbal.
  • When giving Synthroid to children, schedule frequent doctor visits, thus, allowing the doctor to keep an eye on your child’s progress. This is important because children are more likely to experience the side effects that are attached to taking Synthroid.


  • Also, when giving Synthroid to the elderly, take special care of them as just like children, they too are more sensitive to the adverse effects of this medicine.
  • Present research indicates that you can consume Synthroid while pregnant. However, it is still recommended that you inform your doctor if you are pregnant. Your doctor may want to make some changes to the dosage of this medicine.
  • This medicine is also known to pass down into breast milk. Although Synthroid is not known to harm an infant, still, it is better that you inform your doctor if you are breastfeeding.