The long-term side effects of thyroid medication include weight fluctuations, decreases in bone mineral density, sensitivity to heat, joint pain, changes to your menstrual cycle, and possibly even autoimmune dysfunction.
It's helpful to understand what happens in the body after you take levothyroxine. Once the medication enters your bloodstream, the T4 hormone is converted into T3 (triiodothyronine). This is the “active” form of the hormone that does the work, says King. This medication can be finicky, though.
It's one of the most common medications in the U.S. Common side effects of levothyroxine include heat intolerance, a fast heart rate, and diarrhea.
Yes, it's safe to take levothyroxine for a long time, even many years. However, high doses of levothyroxine over a long time can sometimes cause weakening of the bones (osteoporosis). This should not happen if you are on the right dose. It's important to have regular blood tests to make sure your dose is not too high.
Levothyroxine is generally taken life-long when used to treat hypothyroidism (low thyroid levels) unless the cause is transient.
If you stop your thyroid medication abruptly, symptoms of hypothyroidism will likely return. If hypothyroidism is left untreated, it can lead to serious health problems. You may experience mood swings, irritability, and slowed thoughts. In fact, hypothyroidism is one of the reversible causes of dementia.
For people with heart problems: Levothyroxine can increase your risk of serious heart problems, such as heart attack, abnormal heart rhythm, and heart failure. This risk is increased if you've already had these problems. Tell your doctor if you have heart problems or a history of heart problems.
levothyroxine food
In addition, absorption of levothyroxine may be decreased by foods such as soybean flour, cotton seed meal, walnuts, dietary fiber, calcium, and calcium fortified juices. These foods should be avoided within several hours of dosing if possible.
Levothyroxine may cause serious or life-threatening problems when given in large doses, especially when taken with amphetamines such as amphetamine (Adzenys, Dyanavel XR, Evekeo), dextroamphetamine (Dexedrine), and methamphetamine (Desoxyn).
Levothyroxine-induced liver injury is a rare and reversible adverse effect. Clinical vigilance is required when initiating the drug. Triiodothyronine is an appropriate alternative to levothyroxine in treating such cases.
Thyroid Hormone Replacement
Other medications are also available, namely liothyronine, a synthetic version of another thyroid hormone called triiodothronine (T3); liotrix, a synthetic combination of T4 and T3; and desiccated natural thyroid (natural thyroid hormone prepared from dried porcine [pig] thyroid).
Levothyroxine is generally well-tolerated, but it still has the potential to cause side effects. Heat intolerance, sweating, and diarrhea have been reported, especially when you're first starting the medication or changing doses.
When your doctor asks you to stop your thyroid medication, your hormone level will decrease significantly, and this may lead to signs and symptoms of acute hypothyroidism. Weakness, lethargy, cold intolerance, paleness, dry skin, coarse hair, and constipation can occur with acute hypothyroidism.
Treatment with levothyroxine was associated with a delay in progression to CKD stage 5 or ESRD, as well as overall renal function preservation [10].
What happens when you stop taking thyroid medication? If you stop taking your thyroid medication, you can expect your hypothyroid symptoms to return. Typically, the longer you go without your medication, and the more severe your thyroid disease is, the higher your risk for severe and even life-threatening conditions.
Dairy products—including milk, cheese and yogurt—contain high calcium levels, which affect how levothyroxine is absorbed into your body. Drinking milk or eating other calcium-rich foods less than 4 hours before or after taking levothyroxine can reduce the absorption of the drug, lowering its efficacy.
This can cause your T4 hormone levels to drop or fluctuate. To avoid this, levothyroxine should be taken on an empty stomach, and you should wait an hour before eating anything or drinking a caffeinated beverage.
Cardiac arrhythmias and the deterioration of osteoporosis are the most frequently documented side-effects of LT4 therapy. It also lowers the threshold for the onset or aggravation of cardiac arrhythmias for patients with pre-existing heart diseases.
When you start levothyroxine you won't feel better the next day. You may not feel better in two weeks. But symptoms should start disappearing within a month. After six weeks of treatment, you should be almost completely free of symptoms, assuming you're at the right medication level.
The dose is usually 1.7 microgram (mcg) per kilogram (kg) of body weight per day but may be less in older adults. Children older than 12 years of age (growth and puberty incomplete)—Dose is based on body weight and must be determined by your doctor. The dose is usually 2 to 3 mcg per kg of body weight per day.
If you miss one or two doses
Most thyroid hormone medications last in your body for several days. So if you take it every day and miss just one or two doses, you probably won't feel any different.
Summary. Not taking your hypothyroid or hyperthyroid medication can cause undesirable, dangerous, and even life-threatening conditions, ranging from fatigue and changes in blood pressure to death.
The half-life (time taken for amount of drug in your body to be reduced by half) of levothyroxine is 6 - 7 days in euthyroid, 9 - 10 days in hypothyroid and 3 - 4 days in hyperthyroid. So, it would take few weeks for your body to get rid of the thyroid medication.