Written by &you Labs Team
Updated August 9, 2026
Has anyone ever told you "your thyroid is normal," while you still felt tired, could not lose weight, had brain fog, lost hair, or always felt cold? That "normal" probably meant just one number: TSH, checked against a wide range. A real thyroid check needs more than one number.
This guide walks through the full thyroid panel. It covers what each marker reveals, the gap between the "normal" TSH range and the healthy target range, and how to read common patterns.
A full thyroid panel includes TSH, Free T3, Free T4, and, when needed, Reverse T3 and thyroid antibodies. TSH alone is the most common thyroid test ordered in the Philippines. On its own, it misses an underactive thyroid that has not become severe yet, problems converting one hormone to another, and autoimmune thyroid disease.
Your brain's pituitary gland releases TSH, short for thyroid-stimulating hormone. This tells your thyroid gland how much hormone to make. Your thyroid makes mostly T4, a hormone that starts out inactive. It also makes a smaller amount of T3, the active hormone. Your body converts T4 into T3 in tissues throughout your body. It also makes Reverse T3, an inactive twin of T3 that acts as a brake.
A real thyroid check needs at least three numbers. The brain's signal, TSH. The starting hormone, Free T4. And the active hormone, Free T3.
This measures your pituitary's signal to your thyroid. The standard range is 0.4 to 4.5 mIU/L. The healthy target is 0.5 to 2.5 mIU/L. This range is wide because labs build it from population averages. Many thyroid specialists argue the upper limit should be tighter. They suggest closer to 2.5 or 3.0 mIU/L, based on outcome research.
Here is what different results can mean:
A TSH of 4.0 counts as "normal" on most Philippine lab reports. But this is also the zone where many people already have real symptoms.
This measures the active, usable form of T4, the starting hormone. The standard range is 0.8 to 1.8 ng/dL. The healthy target sits in the middle of that range, though the exact target can vary by lab. Free T4 is what your body has available to convert into T3. Low Free T4 alongside a high TSH is the classic pattern for a true underactive thyroid.
This measures the active, usable form of T3, your active thyroid hormone. The standard range is 2.3 to 4.2 pg/mL. The healthy target sits in the upper part of that range. Here is where your Free T3 and Free T4 should actually land. Free T3 is the most active thyroid hormone your body uses. Many doctors who use the optimal-range approach see it as the single most useful thyroid number for matching symptoms.
Here is a common pattern: normal TSH, normal Free T4, but low Free T3. This points to a conversion problem. Your body is making enough T4. It is just not turning enough of it into T3. Causes include low selenium, zinc, or iron. Chronic stress, very low-calorie diets, gut inflammation, and ongoing illness can cause it too.
This measures an inactive twin of T3. It competes with real T3 for space on your cells. Doctors often test it when symptoms continue despite a "normal" TSH and Free T4. A high rT3 acts like a brake. It blunts the effect of the active T3 you do have. It tends to rise with chronic stress, illness, severe dieting, or recovery from a major injury.
The ratio between Free T3 and Reverse T3 gives a useful picture of how much active thyroid hormone your tissues can actually use.
These tests look for signs that your immune system is attacking your thyroid.
High antibodies can show up years before your TSH changes at all. Someone with positive TPO antibodies and a high-normal TSH is on a trend worth tracking and treating early.
TSH of 4.5 to 10 mIU/L. Free T4 normal. Free T3 normal to low. Symptoms vary: fatigue, weight gain, feeling cold. Often an early form of Hashimoto's disease.
TSH above 10 mIU/L. Free T4 below range. Free T3 below range. Symptoms are clear, and treatment is needed.
TSH normal. Free T4 normal or high-normal. Free T3 low. Reverse T3 sometimes high. Symptoms show up despite a "normal" TSH. Common with chronic stress, dieting, or ongoing illness.
TSH can be high, low, or normal. TPO or TgAb antibodies test positive. Often a thyroid pattern that swings over the years.
TSH very low, under 0.1. Free T4 and Free T3 both high. TRAb antibodies often positive. Symptoms include weight loss, a racing heart, anxiety, and feeling too warm.
A standard physical exam in the Philippines that checks "thyroid testing" usually means TSH alone. This catches a severe underactive thyroid. It also catches a severe overactive thyroid.
It misses a lot, though. It misses an early underactive thyroid with real symptoms, a TSH of 2.5 to 4.5. It misses conversion problems, where Free T3 is low but TSH looks normal. It misses autoimmune thyroid disease, since antibodies can show up before TSH moves. It misses a high Reverse T3 during stress or illness.
Many Filipinos with real thyroid symptoms get told their thyroid is fine.
Strongly consider asking for Free T3, Free T4, and antibodies, alongside TSH, if you have any of these:
Making and converting thyroid hormone depends on nutrients that are often low in diets across the region.
Stress, eating too little, poor sleep, and high inflammation (a high hs-CRP) all get in the way of conversion and raise Reverse T3.
For a clearly underactive thyroid, treatment is usually levothyroxine, a T4-only medicine. Some people with ongoing symptoms do better on a combination of T4 and T3. This should always be a decision made with your doctor.
For an early underactive thyroid with symptoms, or positive antibodies, more doctors now recommend treatment even when TSH sits in the upper end of the normal range.
For Graves' disease and other overactive thyroid conditions, treatment options include medicine, radioactive iodine, or surgery. This is also a decision for your doctor to guide.
A &you Labs panel is built to look at your thyroid more fully than TSH alone. Every result comes with the standard lab range and the healthy target range side by side, plus a doctor's written interpretation of any patterns across your thyroid markers.
Cost is the usual reason. TSH alone is cheaper and catches the most severe cases. Most doctors agree the full panel gives more information. It is mostly a coverage limit, not a medical disagreement.
TSH shifts through the day. A first-morning sample, around 6 to 8 AM, gives the most reliable reading for tracking over time. Try to test at the same time each time.
This varies. Some doctors want you to skip your morning dose until after the draw. Others want you to take your normal dose. Follow your own doctor's instructions.
A positive TPO result with a normal TSH is a yellow flag, not a diagnosis. It flags a higher chance of developing Hashimoto's disease later, and it supports closer monitoring.
TSH usually settles about 6 to 8 weeks after each dose change. Symptoms often start improving within a few weeks, but full improvement can take several months. Your doctor should recheck Free T3 and Free T4 at your follow-up too.
The &you Labs Team combines medical science with personal care. We help Filipinos understand their health markers with blood work analysis that is easy to follow, whole person support, and health expertise built for Filipino life.
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