Staying with Synthroid

Your doctor chose Synthroid for you to help replace the thyroid hormone (thyroxine) your body needs. If you take it exactly as prescribed, Synthroid can help bring your thyroxine level back into balance.

Not all thyroid medicines are the same

Synthroid is a type of medicine called levothyroxine sodium. The FDA has approved several levothyroxine products to treat hypothyroidism. The FDA has also determined that some, but not all, of these products are therapeutically interchangeable.

If you change to a product that is not interchangeable with Synthroid,
you may not get the precise amount of levothyroxine your body needs

Even a tiny change in the amount of levothyroxine your body absorbs can affect your TSH level and how you feel. This may cause symptoms of underreplacement or overreplacement. You may need a follow-up blood test in 6 to 12 weeks to make sure that your TSH level is in balance. If it is not, the doctor may have to adjust your dose.

Be alert to the signs of underreplacement or overreplacement

Not getting the amount of levothyroxine your body needs is called underreplacement.

Getting more levothyroxine than your body needs is called overreplacement.

Symptoms of underreplacement

Symptoms of overreplacement
  • Feeling very tired or sluggish
  • Weight gain
  • Dry skin
  • Depression
  • Cold hands and feet
  • Problems with memory and thinking
  • Feeling nervous or jittery
  • Weight loss
  • Anxiety
  • Fast heart beat
  • Sweating too much

Underreplacement can lead to problems with pregnancy, changes in blood cholesterol levels, heart attacks in older women, and other health conditions.

Overreplacement can lead to weak bones, changes in how your heart beats (atrial fibrillation), and other health conditions.

Ask your doctor about the importance of staying with the Synthroid brand

If you switch, you may get a different levothyroxine product with each refill.

You could get one manufacturer's product this month and a different one when you get a refill. Every time you take a different product, it may affect your TSH level if the new medicine you receive is not interchangeable with Synthroid.

Ask your doctor to write "Dispense as Written" (or your state's language for specifying no substitutions) on your Synthroid prescription. This ensures that you always get Synthroid when you refill your prescription.

Check your pills every time you refill your prescription. Be sure your pill says "Synthroid." If it doesn't say "Synthroid," it's not Synthroid

Next >> Talking with your pharmacist