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Taking thyroid medication regularly every day is important for people who have thyroid conditions. But life gets busy, and it’s easy to forget a dose. Missing one dose of your thyroid medication is typically not a big deal. However, missing doses or skipping doses frequently can affect your thyroid hormone levels and cause severe adverse effects. 

Please keep reading to find out what happens if you miss a dose of thyroid hormone treatment and how you can avoid missing doses.

What medications are used to treat low and high thyroid hormones?

There are two main types of thyroid disorders— hypothyroidism (underactive thyroid or decreased thyroid function) and hyperthyroidism (overactive thyroid or increased thyroid function). Thyroid patients may, therefore, be prescribed the following thyroid drugs:

Drugs used to treat hypothyroidism (underactive thyroid disease)

These drugs are used to return thyroid hormone levels to normal in hypothyroid patients who don’t make enough thyroid hormones. They may also be used to treat certain types of thyroid cancer, along with thyroid surgery and radioiodine therapy.

• Levothyroxine (synthetic thyroid hormone T4)

• Liothyronine (synthetic thyroid hormone T3)

• Liotrix (combination of T3 and T4)

• Desiccated thyroid extract (DTE) (T3 and T4 from animal thyroid glands)

Drugs used to treat hyperthyroidism (overactive thyroid disease)

These anti-thyroid medicines are used to prevent the thyroid from making too much thyroid hormone.

• Methimazole 

• Propylthiouracil 

What happens if I miss one day of my thyroid medication?

Missing a day of your thyroid medication does not usually cause any problems. If you accidentally skip or miss a dose, take it as soon as you remember. However, if it is almost time for the next dose, skip the missed dose and go back to your regular dosing schedule. Do not take a double dose or extra medicine to make up for a missed dose.

Note: If you forget to take a dose of your thyroid medication and are taking it later in the day, remember your doctor’s dosing instructions. For example, you should take:

• Levothyroxine on an empty stomach (certain foods can affect absorption of this medicine).

• Methimazole with food or milk (taking it on an empty stomach can cause stomach upset).

How long can you last without thyroid medication?

You can last a week or so without thyroid medication before you will likely see a return of your symptoms. How soon your symptoms return depends on various factors, such as the condition being treated, its severity, the dose of thyroid medication, and how quickly your body eliminates thyroid medications from the system. 

What happens if you stop taking levothyroxine (hypothyroid treatment)?

Levothyroxine has a half-life of 6-7 days. This means the blood concentration of levothyroxine falls to half its original value after 6-7 days. It takes the body 4-5 weeks to completely eliminate the drug. However, you may start experiencing symptoms of mild hypothyroidism within a week of stopping levothyroxine. These symptoms will gradually get worse if you do not resume levothyroxine treatment.

Note: Stopping your thyroid medication (levothyroxine) for a very long period can put you at risk of a condition called myxedema coma, in which the body’s functions become dangerously slow, requiring emergency treatment.

You will likely need to take levothyroxine for life. In addition, your doctor will order regular blood tests (TSH levels) to check thyroid hormone levels. Keep all your medical and lab appointments and set a daily reminder to help you remember to take your medicine. Find out: “How Long Does Levothyroxine Stay in Your System?”

What happens if you stop taking anti-thyroid medicine (hyperthyroid treatment)?

The half-life of anti-thyroid medications is 3-5 hours (methimazole) and 1-2 (propylthiouracil). This means the body gets rid of these thyroid medications in less than 24 hours. Missing several doses of anti-thyroid medications can cause your hyperthyroidism symptoms to return. You should not stop thyroid medication without talking to your healthcare professional. 

Find out: “How Long Does It Take for Levothyroxine to Work?”

What happens if you take 2 thyroid pills in one day by mistake?

Taking 2 thyroid pills in one day by mistake does not usually cause any major problems. However, you should call your doctor immediately or seek emergency medical attention if you develop the following symptoms:

Symptoms of levothyroxine overdose

• Chest pain

• Shortness of breath

• Fast or irregular heartbeat

• Anxiety, irritability, nervousness

• Sleep problems

• Uncontrolled shaking

• Confusion

• Seizures

• Loss of consciousness

Symptoms of anti-thyroid medication overdose

• Stomach pain, nausea, vomiting

• Fever

• Headache

• Joint pain

• Swelling of the hands, arms, lower legs, ankles, or feet

• Skin itching, blistering, or peeling

• Signs of infection (fever, chills, sore throat)

• Unusual bleeding or bruising

• Loss of appetite, right upper stomach pain, yellowing of the skin or eyes

• Numbness or burning in the hands or feet

• Excessive tiredness or weakness

Learn about some of the long-term side effects of levothyroxine.

What are the symptoms if your thyroid medication is too low?

If you are taking levothyroxine for an underactive thyroid gland and your medication is too low, you may experience the following symptoms of hypothyroidism:

• Fatigue

• Weight gain

• Cold intolerance

• Constipation

• Joint and muscle pain

• Dry skin, hair loss, thinning hair

• Irregular periods or heavy menstrual periods

• Depression

• Slowed heart rate

Note: Thyroid medication can interact with certain medications and this can affect how well it works. Give your healthcare provider a complete list of your other drugs and supplements to avoid potential interactions. Also, certain foods like soy and dietary fiber can interfere with levothyroxine absorption. Talk to your doctor about potential food and drug interactions if you feel your thyroid medicine is too low. Check out our blog: “What Are Some Signs My Thyroid Medication Is Not Working?”

What are the symptoms if your thyroid medication is too high?

If you are taking levothyroxine for an underactive thyroid and your medication dose is too high, you can develop symptoms of hyperthyroidism (overactive thyroid), such as:

• Heart palpitations (fast or irregular heartbeat)

• Shakiness

• Muscle weakness

• Frequent bowel movements

• Weight loss despite an increased appetite

• Trouble sleeping, nervousness, irritability

• Heat intolerance or excessive sweating

Keep all your laboratory appointments while on levothyroxine. Your doctor will adjust your dose based on TSH levels. Learn about levothyroxine's side effects.

Tips to remember to take your thyroid medication

• Take your medication at around the same time every day; for levothyroxine, it is best to take it first thing in the morning before eating breakfast.

• Set a reminder on your phone.

• Keep your thyroid medication in a visible place, such as your bedside table or kitchen counter (but keep all medications safely out of reach of children and pets).

• Use a pill organizer.