Your thyroid labs: a cheat sheet to bring to your doctor

This is a quick reference to help you understand your own thyroid labs and make better sense of them, so you can walk into your appointment with clearer questions. It is education, not medical advice, and not me acting as your doctor. Your prescriber makes every medication decision, and how you feel always counts alongside the numbers. And hold the rule underneath all of it: normal is not the same as optimal.

This sits alongside the fuller picture in 'The Full Thyroid Panel: Getting the Complete Picture' and the woodworking shop image in 'What Your Thyroid Does, and What Changes When It Does Not Work'.

If the numbers feel like a lot, that is alright. Take a slow breath into your belly, and let your belly expand. This diaphragmatic breathing genuinely helps to calm the nervous system. You are simply learning to read your own body.

The optimal targets to aim for

Read these against the printed range on your own report, because labs differ. 'Upper third' and 'upper half' just mean toward the top of whatever range your report shows.

• TSH: about 0.5 to 1.0, a calm, low number. If you take a medication that contains T3, a TSH below 0.5 is normal and expected, so a low TSH by itself is not a red flag.
• Free T4: the upper half of the range.
• Free T3: the upper third of the range. This is the one most tied to how you feel.
• Reverse T3: near the bottom of the range, a common rule of thumb is under 15.
• Free T3 to Reverse T3 ratio: above 20.
• TPO antibodies (TPOAb) and thyroglobulin antibodies (TgAb): as low as possible. Remission looks like TPOAb under 9 and TgAb under 1.

What your results may point to

This shows how the pattern of your numbers points toward a conversation. It is not a set of instructions, and nothing here is a reason to change a medication on your own. Bring it to the person who prescribes for you, and let them make the call from your whole picture.

• If Free T4 is low, toward the bottom or lower-middle of the range, there may not be enough raw material. This points to a conversation about your T4 (levothyroxine, or a cleaner option like Tirosint).
• If Free T4 looks good but Free T3 is low, you have the raw material and are not turning it into the active hormone. This points to a conversation about conversion: lowering stress, and covering the nutrients it needs, such as selenium, zinc, and iron, and sometimes about whether T3 (liothyronine) belongs in the picture.
• If Reverse T3 is high, around 15 or above, and the ratio is low, around 20 or below, too much is being wasted, usually driven by stress. This points to a conversation about calming the stress drivers, and sometimes about whether the balance of T4 and T3 in your treatment is worth revisiting with your prescriber.
• If TSH is above your optimal zone with low Free T3 and Free T4, and you feel tired, that is the undermedicated picture. This points to a conversation about more thyroid support.
• If Free T3 and Free T4 are running high and you feel wired or have palpitations, that may be too much, and points to a conversation about easing back. One reminder: if you are on a T3 medication, a low TSH on its own does not mean too much. It is the Free T3, the Free T4, and how you feel that tell the real story.

The one-line version to keep in your pocket

• Low Free T4 points to a T4 conversation.
• Low Free T3 with adequate Free T4 points to a T3 and conversion conversation.
• High Reverse T3 points to a stress and conversion conversation, and sometimes to revisiting the T4 and T3 balance with your prescriber.

Before you leave the lab

Make sure the panel included all 6: TSH, Free T4, Free T3, Reverse T3, TPO antibodies (TPOAb), and thyroglobulin antibodies (TgAb). Ask for a copy of your results, and bring the actual numbers to your appointment.

You are allowed to ask for the full panel, and you are allowed to ask again. Understanding your own numbers is not stepping on your doctor's toes. It is showing up to the conversation as a real partner in your own care.

---