Dr. Sheldon Rubenfeld Board Certified in Internal Medicine and in Endocrinology, Diabetes, and Metabolism

Dosage and Followup

The exact dosage of levothyroxine required by patients must be individually determined. Taking extra levothyroxine will not make the symptoms of hypothyroidism go away any faster, and it may be harmful. Some patients may be tempted to take extra levothyroxine to lose weight. Thyroid hormone can cause weight loss—but only if taken in excess. People who take excessive thyroid hormone to lose weight become hyperthyroid. Much of the weight hyperthyroid patients lose is muscle mass, not fat. In addition to losing muscle mass, these patients risk losing their hair, developing irregular heartbeats, and experiencing other unpleasant symptoms.

Successful treatment with levothyroxine requires that patients take it as directed by their physicians. Levothyroxine is best absorbed when taken with water and on an empty stomach, either one hour before or two hours after a meal. Taking levothyroxine this way is recommended because levothyroxine absorption is decreased by some foods, such as those containing large amounts of either fiber or soybean products (for example, tofu and soy milk.) In addition to food, certain drugs and supplements may interfere with levothyroxine absorption.

Follow-Up Visits

After patients begin levothyroxine therapy, their physicians will perform physical examinations and request thyroid function tests every six to twelve weeks until the correct dosage is determined. On average, a patient’s maintenance dosage of levothyroxine is changed once every three years for one reason or another. These reasons include:

• pregnancy
• estrogen replacement therapy for menopause
• birth control pills containing estrogen
• drugs or food interfering with absorption
• drugs
• iodinated dyes and over-the-counter supplements interfering with thyroid function or tests
• aging
• noncompliance
• the variable nature of the underlying thyroid disease
• changes in the prescribed brand-name levothyroxine\decrease in potency of stored levothyroxine
• malabsorption of levothyroxine (rare)

The onset of hypothyroidism is slow and insidious. Similarly, a full response to treatment occurs gradually and may take six weeks or more. Hypothyroid patients should not expect immediate improvement, even if the initial dosage of levothyroxine is correct.