The symptoms of hypothyroidism can be different from person to person. And they often look like symptoms of other health problems. Because of that, a diagnosis of hypothyroidism doesn't rely on symptoms alone. It's usually based on the results of blood tests.

The first blood test typically done to diagnose hypothyroidism measures the level of thyroid-stimulating hormone (TSH) in the blood. If it's high, the test is done again, along with a blood test for the thyroid hormone T-4. If the results show that TSH is high and T-4 is low, then the diagnosis is hypothyroidism. In some cases, the thyroid hormone T-3 may be measured as well.

If the second test shows high TSH but T-4 and T-3 are in the standard range, then the diagnosis is a condition called subclinical hypothyroidism. It usually doesn't cause any noticeable symptoms.

TSH tests also play an important role in managing hypothyroidism over time. They help your health care provider find and maintain the right dosage of medication for you.

The results of these blood tests can be affected by some medicines or supplements. This includes biotin, a vitamin taken as a stand-alone supplement or as part of a multivitamin. Before you have blood tests done, tell your health care provider about any medicines or supplements you take.


Treatment for hypothyroidism usually includes taking the thyroid hormone medicine levothyroxine (Levo-T, Synthroid, others) every day. This medicine is taken by mouth. It returns hormone levels to a healthy range, eliminating symptoms of hypothyroidism.

You'll likely start to feel better one or two weeks after you begin treatment. Treatment with levothyroxine likely will be lifelong. Because the dosage you need may change, your health care provider may check your TSH level every year.

Finding the right dosage

To find the right dosage of levothyroxine for you, your health care provider checks your level of TSH about 6 to 8 weeks after you start taking the medicine. You may need another blood test to check TSH again six months later. Too much levothyroxine can cause side effects, such as:

  • Tiredness.
  • Increased appetite.
  • Sleep problems.
  • Shakiness.
  • Pounding of the heart, sometimes called heart palpitations.

Levothyroxine typically causes no side effects when used in the correct dose. If you change brands of the medicine, tell your health care provider, as the dosage may need to change.

If you have coronary artery disease or severe hypothyroidism, your health care provider may start treatment with a smaller amount of medicine and then slowly increase the dosage. This allows your heart to adjust to the rise in your body's metabolism.

Taking levothyroxine correctly

Levothyroxine is best taken on an empty stomach at the same time every day. Ideally, you take the hormone in the morning, and then wait 30 to 60 minutes before you eat or take other medicine. If you take the medicine at bedtime, wait to take it until at least four hours after your last meal or snack.

Don't skip doses or stop taking the medicine because you feel better. If you do, it's likely that the symptoms of hypothyroidism will slowly return. If you miss a dose of levothyroxine, take two pills the next day.

Some medicines, supplements and even some foods may affect your body's ability to absorb levothyroxine. Talk to your health care provider if you eat large amounts of soy products, or if you typically eat a high-fiber diet. Also, tell your provider if you take other medicines, especially:

  • Iron supplements or multivitamins that contain iron.
  • Aluminum hydroxide, which is found in some antacids.
  • Calcium supplements.

Subclinical hypothyroidism

If you are diagnosed with subclinical hypothyroidism, talk about treatment with your health care provider. For a mild rise in TSH, thyroid hormone medicine may not be useful. If your TSH level is higher, but still in the subclinical range, thyroid hormones may improve some symptoms.

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Alternative medicine

Most health care providers recommend taking the medicine levothyroxine to treat hypothyroidism. But an extract containing thyroid hormone derived from the thyroid glands of pigs is available. It is sometimes called desiccated thyroid extract. However, this treatment is not recommended because the amount of T-4 and T-3 in it may not be consistent from batch to batch. It is not safe for pregnant people to take desiccated thyroid extract because it can harm a fetus's development.

Preparing for your appointment

You'll likely start by seeing your primary health care provider. Or you may be referred to a specialist in hormone disorders, called an endocrinologist. Infants with hypothyroidism need to see a pediatric endocrinologist right away. Children or teens can start with their primary health care provider. But they need to see a pediatric endocrinologist if there are any questions about levothyroxine or about the correct dosage of the medicine.

Here's information to help you get ready for your appointment and know what to expect from your health care provider.

What you can do

  • Be aware of any pre-appointment restrictions. When you make the appointment, ask if there's anything you need to do before you arrive.
  • Write down any symptoms you're experiencing, including any that may seem unrelated to the reason you scheduled the appointment.
  • Write down key personal information, including any major stresses or recent life changes.
  • Make a list of all medicines, vitamins or supplements you're taking.
  • Take a family member or friend along, if possible. Someone who goes with you may remember something that you missed or forgot.
  • Write down questions to ask your health care provider.

Having a list of questions helps you make the most of your time with your health care provider. For hypothyroidism, some basic questions to ask include:

  • What's the most likely cause of my symptoms?
  • What tests do I need?
  • Is my condition likely temporary or long lasting?
  • What treatments are available, and which do you recommend?
  • I have other health conditions. How can I best manage them together?
  • Are there restrictions I need to follow?
  • Should I see a specialist?
  • Is there a generic alternative to the medicine you're prescribing?
  • Are there brochures or other printed material I can take with me? What websites do you recommend?

Don't hesitate to ask other questions.

What to expect from your doctor

Your health care provider is likely to ask you a number of questions, including:

  • When did you begin experiencing symptoms?
  • Have your symptoms been continuous or occasional?
  • How severe are your symptoms?
  • What, if anything, seems to improve your symptoms?
  • What, if anything, makes your symptoms worse?
  • Do you have a family history of thyroid disease?
Dec. 10, 2022
  1. AskMayoExpert. Hypothyroidism. Mayo Clinic; 2021.
  2. Hypothyroidism. American Thyroid Association. https://www.thyroid.org/hypothyroidism/. Accessed Nov. 10, 2022.
  3. Loscalzo J, et al., eds. Hypothyroidism. In: Harrison's Principles of Internal Medicine. 21st ed. McGraw Hill; 2022. https://accessmedicine.mhmedical.com. Accessed Nov. 10, 2022.
  4. Hypothyroidism. National Institute of Diabetes and Digestive and Kidney Diseases. https://www.niddk.nih.gov/health-information/endocrine-diseases/hypothyroidism. Accessed Nov. 10. 2022.
  5. Ross DS. Diagnosis of and screening for hypothyroidism in nonpregnant adults. https://www.uptodate.com/contents/search. Accessed Nov. 10, 2022.
  6. Surks MI. Clinical manifestations of hypothyroidism. https://www.uptodate.com/contents/search. Accessed Nov. 10, 2022.
  7. AskMayoExpert. Congenital hypothyroidism (child). Mayo Clinic; 2021.
  8. Hyperthyroidism in infants and children. Merck Manual Professional Version. https://www.merckmanuals.com/professional/pediatrics/endocrine-disorders-in-children/hypothyroidism-in-infants-and-children. Accessed Nov. 10, 2022.
  9. Ross DS. Hypothyroidism during pregnancy: Clinical manifestations, diagnosis, and treatment. https://www.uptodate.com/contents/search. Accessed Nov. 10, 2022.
  10. Brito Campana JP. (expert opinion). Mayo Clinic. Nov. 16, 2022.

Hypothyroidism (underactive thyroid)