Thyroid Hormone Levels Explained

Ever looked at a lab report and wondered what the numbers next to TSH, T3, and T4 mean? They’re the clues your body gives about how the thyroid is working. In plain terms, thyroid hormones control how fast or slow your metabolism runs. When the levels are off, you can feel sluggish, jittery, or somewhere in between.

What’s a Normal Range?

Most labs list a normal TSH range of about 0.4 to 4.0 mIU/L. Free T4 usually falls between 0.8 and 1.8 ng/dL, and free T3 sits around 2.3 to 4.2 pg/mL. Those numbers aren’t set in stone; they shift a bit with age, pregnancy, and lab methods. The key is to look at the trend, not just a single value.

If TSH is high and T4 is low, your doctor will likely call it hypothyroidism – the thyroid isn’t making enough hormone. The opposite—low TSH and high T4/T3—points to hyperthyroidism, where the gland is over‑active.

How to Manage Low or High Levels

For hypothyroidism, most people start on levothyroxine, a synthetic T4 pill that mimics the hormone you’re missing. Take it on an empty stomach, wait 30 minutes, and avoid iron or calcium supplements right after – they can block absorption.

Hyperthyroidism often needs medication like methimazole, radioactive iodine, or even surgery in severe cases. Your doctor will pick the option that fits your age, symptom severity, and overall health.

Beyond prescription drugs, lifestyle tweaks can help balance hormones. A diet rich in selenium (found in Brazil nuts) and iodine (seafood, iodized salt) supports thyroid production. Too much soy or highly processed foods can interfere, so keep those to a moderate level.

If you have hypothyroidism, constipation is a common side effect. Simple changes—adding more fiber, drinking plenty of water, and moving around after meals—can ease the issue. Our article on “How to Manage Constipation with Hypothyroidism and Hyperthyroidism” dives deeper into diet and timing tricks.

Stress and sleep matter, too. Chronic stress spikes cortisol, which can blunt thyroid hormone conversion. Aim for 7‑8 hours of quality sleep and try relaxation techniques like breathing exercises or short walks.

Regular check‑ups are a must. Your doctor will likely re‑test TSH every 6‑12 months after starting or adjusting medication. If you feel better but the numbers still look off, discuss the goal range with your provider – sometimes a slightly different target works best for you.

Remember, thyroid health is a marathon, not a sprint. Small, consistent moves – taking meds as prescribed, eating a balanced diet, staying active, and keeping stress low – add up to a smoother metabolism and more energy.