This is one of the most common stories I hear. Two, five, ten years on thyroid medication. The TSH is controlled and the prescriber is satisfied. And the person in front of me is still worn out in a way sleep does not touch, still foggy, still fighting their weight, still losing hair. These are the six places I look.

1. Whether the cause is Hashimoto's

Most hypothyroidism in developed countries comes from Hashimoto's, an autoimmune disease.1 Hormone replacement fixes the shortage the disease creates. It does nothing to the immune activity behind it, which is how a controlled TSH and a bad year can happen at the same time. If nobody has checked your TPO and thyroglobulin antibodies, start there. Keep the purpose clear, though: antibodies tell you the process is autoimmune. They are not the outcome to chase. How you feel is.

2. Free T3 and reverse T3

Levothyroxine is T4, the inactive form. Your body still has to convert it into T3. Low free T3 can leave you feeling hypothyroid with a perfect TSH, and high reverse T3, which rises under stress and inflammation, can block T3 from doing its job. Cortisol itself suppresses the converting enzyme.2 A TSH-only follow-up will never show any of this.

3. Your stomach, and H. pylori

Levothyroxine needs stomach acid to dissolve before it can be absorbed. H. pylori, a common stomach bacterium, causes gastritis that lowers acid. In a New England Journal of Medicine study, people with H. pylori gastritis, atrophic gastritis or both needed 22 to 34 percent more thyroxine than a reference group, and clearing the infection largely reversed that.3 If your dose keeps creeping up and your TSH still will not settle, ask about a stool antigen or breath test for H. pylori. Those detect active infection better than a blood antibody test.

4. Iron, B12 and vitamin D

These cause the same tiredness and fog as a struggling thyroid, and they are cheap to check. Iron is the one I see missed most. In a randomized trial of menstruating women with a ferritin under 50 and no anemia, fatigue fell about 48 percent with oral iron against 29 percent with placebo.4 For B12, ask whether methylmalonic acid can be added, since a normal serum B12 can hide a shortfall at the cell level.

5. Celiac disease

Hashimoto's raises your risk of celiac disease. Celiac is a real diagnosis with a treatment that works, and the blood test only works while you are still eating gluten. So test first. If it is positive, a strict gluten-free diet is the treatment. If it is negative, a gluten-free trial is still reasonable, but run it as an experiment for 8 to 12 weeks and judge it by how you feel. The research on gluten-free diets in Hashimoto's without celiac is mixed enough that gluten is best treated as a possible factor, not a proven one for everyone.5

6. Sleep and stress

Sleep that looks long enough on paper can still be shallow and broken. Loud snoring, pauses in breathing or waking up gasping deserve a conversation about a sleep study, because sleep apnea is treatable and persistent daytime sleepiness is one of its signs. Long-running stress belongs on this list too, for the conversion reason in point 2.

On your medication. Nothing here asks you to stop, lower or change your thyroid medication. That decision belongs to you and your prescriber. Everything on this list runs alongside your prescription, not in place of it.

Common questions

Can H. pylori affect thyroid medication?

It can. Gastritis from H. pylori lowers stomach acid, which levothyroxine needs to dissolve. In the study above, affected patients needed 22 to 34 percent more thyroxine, and treating the infection largely reversed it.

Will lowering my TPO antibodies make me feel better?

Not necessarily. Several things lower antibodies, but none has been shown to improve how people feel by doing so. Use antibodies to confirm Hashimoto's and to monitor it, and measure progress by your symptoms.

My TSH is normal but I never had antibodies checked. Should I?

Yes, once. They tell you whether your hypothyroidism is autoimmune, which changes what else is worth looking at. See Normal TSH, but still feel hypothyroid? for the full panel.