Thyroid Medications: What You Need to Know Right Now

If your doctor prescribed a thyroid drug, you probably have questions: which medicine, how much, and what to avoid. This page gives clear, practical advice on common thyroid medicines, how to take them, what interacts with them, and when to call your clinician.

Common drugs and how they work

For low thyroid (hypothyroidism) the go-to medicine is levothyroxine (T4). It replaces the hormone your thyroid no longer makes. Typical doses range from 25 mcg to 200 mcg daily — your doctor picks the right start based on age, weight, and heart health. Liothyronine (T3) is faster-acting and sometimes added for specific cases. Desiccated thyroid (natural extract) is available but varies in strength and isn’t always recommended because dose consistency can be an issue.

For overactive thyroid (hyperthyroidism) common medicines are methimazole and propylthiouracil (PTU). These block hormone production until other treatments—radioactive iodine or surgery—are considered. PTU is usually preferred in the first trimester of pregnancy; methimazole is used outside pregnancy because it has fewer side effects long-term.

How to take them and avoid problems

Take levothyroxine on an empty stomach. Aim for 30–60 minutes before breakfast or at bedtime at least 3–4 hours after your last meal. Consistency matters: take it the same way every day. Calcium, iron, antacids, multivitamins, and some cholesterol drugs can cut absorption. Wait four hours after levothyroxine before taking those supplements or talk to your doctor about timing.

If you switch brands or generics, let your provider know. Lab tests can shift when formulations change. After any dose switch, your doctor will usually check TSH and free T4 in 6–8 weeks to fine-tune dosing. Pregnant people typically need a 20–30% increase in dose right away and closer monitoring during pregnancy.

Watch for signs of taking too much: rapid heartbeat, tremors, anxiety, unexplained weight loss, or more frequent bowel movements. Too little medication shows as tiredness, weight gain, constipation, and feeling cold. If you have heart disease, doctors start lower to avoid stressing the heart.

Drug interactions matter: levothyroxine can increase warfarin effects; amiodarone and lithium can cause thyroid problems; proton pump inhibitors and some antibiotics can change thyroid labs. Herbal products and thyroid extract supplements can be unpredictable — check with your clinician before using them.

Missed a dose? Take it as soon as you remember unless it's near the next dose; then skip and continue normally. Don’t double up. Always keep a clear list of your medicines and bring it to appointments.

When in doubt, contact your provider if you get new symptoms, if you plan pregnancy, or if you change other meds. A few blood tests and small dose tweaks usually keep things steady. With the right plan, most people feel much better on thyroid meds and can get back to normal life fast.