Levothyroxine is a synthetic form of the thyroid hormone thyroxine (T4). It is used to treat hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormone. Levothyroxine is the main treatment for hypothyroidism and is usually taken as a daily tablet. This article provides information on how long someone can safely go without taking their levothyroxine medication.
What is Levothyroxine?
Levothyroxine is a man-made version of the thyroid hormone thyroxine (T4). Thyroxine is produced naturally by the thyroid gland, a small butterfly-shaped gland located at the base of the neck. Thyroxine helps regulate many bodily functions including metabolism, heart rate, mood, and growth and development. Hypothyroidism occurs when the thyroid gland does not make enough thyroxine. Levothyroxine is used to replace the thyroxine that your body is unable to produce on its own. The synthetic T4 in levothyroxine is identical to the natural hormone produced by the thyroid.
Levothyroxine tablets come in different strengths ranging from 25 micrograms (mcg) to 300 mcg. The dose a person needs depends on their weight, age, and other medical conditions. Levothyroxine is taken once a day, ideally first thing in the morning on an empty stomach. This helps with absorption of the medication. It may take several weeks after starting levothyroxine to feel the full effects. Levothyroxine is usually continued for life once hypothyroidism is diagnosed.
How Long Can You Go Without Taking Levothyroxine?
Most people with hypothyroidism cannot safely go for long periods of time without taking their prescribed dose of levothyroxine. However, someone may need to temporarily stop levothyroxine in certain situations outlined below:
- Before thyroid testing: Levothyroxine may be stopped for 2-6 weeks before having thyroid function tests. This allows doctors to get an accurate measure of the thyroid gland’s ability to produce thyroid hormone on its own without the influence of external levothyroxine. Thyroid levels are measured via blood test both before and after stopping medication.
- Before radioiodine therapy: People scheduled to receive radioactive iodine (RAI) therapy are usually asked to stop taking levothyroxine for 2-6 weeks beforehand. RAI treatment involves taking a radioactive iodine pill that gets absorbed by thyroid cells, allowing doctors to visualize or destroy parts of the thyroid. Levothyroxine interferes with this process and is therefore stopped temporarily before RAI administration.
Outside of specific medical procedures, people rely on their daily levothyroxine and should not intentionally skip doses except under a doctor’s direction. But mistakes happen, and you may accidentally miss taking your thyroid medication from time to time. Here is how long you can go without levothyroxine in various scenarios:
Missing 1-2 days
For most people, missing 1 or 2 consecutive days of levothyroxine is unlikely to cause major problems or symptoms. However, there are a few factors to consider:
- The longer you go without levothyroxine, the greater the risk of symptom recurrence. Some people may start experiencing hypothyroid symptoms within 48 hours of missing a dose.
- Individuals on higher levothyroxine doses (e.g. 150-300 mcg daily) are more prone to symptoms if they miss a day or two compared to those on lower doses.
- People who take their levothyroxine inconsistently are more vulnerable to fluctuations in thyroid levels with each missed dose.
- Certain groups including the elderly and those with cardiovascular disease require consistent levothyroxine intake and are more sensitive to changes in thyroid hormone levels.
If you miss a day or two of your thyroid medication, take the missed dose as soon as you remember. Do not double the dose to try to “catch up”. Resume your normal daily dosage the next day and try to avoid further missed doses. Contact your doctor if you experience concerning symptoms.
Missing 3-5 days
Going 3-5 days without taking your prescribed levothyroxine begins entering riskier territory. The longer you go without adequate thyroid hormone replacement, the more likely you are to experience hypothyroid symptoms. Symptoms may include:
- Fatigue
- Brain fog and memory problems
- Depression
- Muscle cramps or weakness
- Constipation
- Dry skin and hair
- Weight gain
- Slowed heart rate
- Feeling cold
- Muscle cramps
Elderly patients and those with heart conditions can experience rapid onset of cardiovascular symptoms like shortness of breath, chest pain, and leg swelling after just a few missed doses. Seek prompt medical attention if you develop any concerning symptom after forgetting to take levothyroxine for a few days in a row.
When you start taking your levothyroxine again after missing 3-5 consecutive days, symptoms should start improving within a few days. However, schedule an appointment with your doctor to assess your thyroid function through bloodwork. Repeat testing may be needed every few weeks until your levels stabilize.Your doctor can help determine if your levothyroxine dose needs adjusting after an extended lapse.
Missing 1-2 weeks
Going without levothyroxine for 1-2 weeks places you at high risk of thyroid hormone withdrawal. Symptoms are likely to be more severe the longer you go without medication. In addition to the hypothyroid symptoms already outlined, other potential problems include:
- Significant fluid retention and swelling (myxedema)
- Decreased body temperature (hypothermia)
- Slow speech, confusion, or memory loss
- Severely slowed heart rate
- Loss of consciousness or coma (myxedema coma)
Myxedema coma is a rare but life-threatening complication of very severe, longstanding hypothyroidism. It requires emergency treatment and hospitalization. Seek immediate medical help if you develop signs of myxedema after going 1-2 weeks without levothyroxine.
Restarting levothyroxine after such a prolonged lapse can be tricky. It takes 6-8 weeks for thyroid hormone levels to fully normalize again. Your doctor will monitor you closely through this period and may start you back on a lower dose to avoid over-replacing thyroid hormone. Be patient as it may take several months for symptoms to fully resolve.
Missing 1 month or longer
Going a month or longer without thyroid hormone replacement is extremely dangerous. Most patients will experience full-blown myxedema symptoms as outlined above. Myxedema coma and death can occur without prompt medical treatment.
If you go a month or more without levothyroxine due to an access issue, contact your doctor’s office immediately to get back on medication before symptoms progress. Thyroid levels take nearly 2-3 months to stabilize after restarting a missed daily dose. Expect regular bloodwork and dose adjustments during this time.
Tips for Not Missing Doses of Levothyroxine
Missing your thyroid medication for an extended period can jeopardize your health. Here are some tips to avoid forgotten levothyroxine doses:
- Take levothyroxine at the same time each morning on an empty stomach.
- Use a weekly pill organizer to pre-sort your doses.
- Keep your levothyroxine next to your toothbrush or on your nightstand to remember your morning dose.
- Set a daily alarm on your phone, watch, or other device to remind you.
- Mark refill dates on your calendar and request refills 1-2 weeks before you run out of pills.
- Inform your doctor if you are having trouble remembering to take your thyroid medication every day.
Also, make sure you understand the signs and symptoms of hypothyroidism. Seek prompt medical care if you develop any hyperthyroid symptoms after missing multiple doses of levothyroxine. Keep your doctor informed about any medication lapses so they can ensure your thyroid levels remain stable.
Who Should Not Go Without Levothyroxine?
Certain groups are at higher risk if they go extended periods without their prescribed levothyroxine:
- Pregnant women – Thyroid hormones are crucial for normal fetal brain development. An untreated thyroid deficiency can cause neurological impairment in the baby.
- Infants and children – Thyroid hormone is essential for growth and development in babies and kids. Missing doses can lead to developmental delays.
- Elderly patients – The elderly are susceptible to myxedema coma if hypothyroidism is untreated. Many older adults have undiagnosed thyroid problems.
- People with heart conditions – Even small changes in thyroid level can destabilize heart function if you have underlying cardiovascular disease.
- Critically ill hospital patients – Stress from trauma, surgery, or infection increases the body’s need for thyroid hormone.
These patient populations should never intentionally skip thyroid medication for an extended time. Work closely with your doctor to ensure continuous levothyroxine coverage based on your health status and risks.
Conclusion
Levothyroxine is an essential medication for people with hypothyroidism. While missing a day or two occasionally may cause only minor symptoms, going for longer periods without thyroid hormone replacement can be dangerous.Aim to take your prescribed levothyroxine dose daily to keep thyroid levels stable. Certain high-risk groups like the elderly, pregnant women, infants, and critically ill patients should never intentionally go more than 1-2 days without medication. Speak with your doctor about any symptoms you experience after forgetting levothyroxine to determine if your dosage or monitoring schedule needs adjustment.