How Do You Lose Weight if You're on Thyroid Hormones?

Last Editorial Review: 9/19/2017

Ask the experts

I have been taking synthroid and I cannot loose weight no matter what I do. Is it OK to take Merida for weight loss if I'm taking Synthroid?

Doctor's response

It is possible that you do have hypothyroidism. You should address your concerns with your physician. To make the diagnosis is quite simple - a blood test in the office is all that's needed. Unfortunately, weight loss is difficult, even if your thyroid is functioning normally. If your blood tests reveal a normal T4 and TSH, taking Synthroid is NOT recommended. If your blood tests reveal a low T4 and an elevated TSH, you do have hypothyroidism, and should be on replacement therapy. If your blood tests reveal a normal T4 but an elevated TSH, you likely have what is referred to as " Subclinical Hypothyroidism". This a condition which often precedes overt hypothyroidism. In this case, there may be benefit to starting you on replacement therapy, and this option should be discussed with your physician.

Regarding the use of Meridia, it is only recommended in people who have a significant amount of weight to loose (a body mass index- or BMI- of greater than 30, or of greater than 27 in the presence of other risk factors). In addition, it is contraindicated in people with high blood pressure, heart failure, or heart disease, and those who are pregnant or breast feeding. Because of its effects on blood pressure, patients are monitored regularly while on Meridia. Side effects of Meridia include:

If you are seriously considering taking Meridia, you should review the side effect profile in detail with your physician. It is also important that you review and set realistic goals with regard to weight loss and maintenance.

Medically reviewed by John A. Daller, MD; American Board of Surgery with subspecialty certification in surgical critical care


"Treatment of primary hypothyroidism in adults"