How to Read Your Thyroid Labs When TSH Looks Normal
How to Read Your Thyroid Labs When TSH Looks Normal?
TL;DR
TSH is a pituitary hormone, not a thyroid hormone. It measures what your brain thinks is happening, not what your cells experience. You can have normal TSH with low Free T3 at the cellular level. Your body temperature and pulse tell you more than blood tests. Track those instead.
Your labs came back normal.
TSH: 2.5. Within range. Your doctor says you're fine.
But you're cold all the time. Exhausted by 2 PM. Gaining weight on the same calories.
"It's not your thyroid," she says. "Your TSH is normal."
Your TSH might be normal. Your thyroid function isn't.
TSH is a memo from your boss. It shows what your boss thinks you should do. It doesn't show what you're actually doing.
What TSH Actually Measures
TSH stands for Thyroid Stimulating Hormone. Your pituitary gland makes it.
When your pituitary detects low thyroid hormone in your blood, it releases TSH. This tells your thyroid to make more hormone.
High TSH means your pituitary is yelling at your thyroid to work harder. Usually indicates hypothyroidism.
Low TSH means your pituitary thinks there's enough thyroid hormone. It stops yelling.
But TSH only measures what's in your blood. It doesn't measure what reaches your cells.
The Problem with TSH-Only Testing
Your thyroid makes T4. T4 is inactive. It's storage.
Your body converts T4 to T3. T3 is active. It enters cells and tells mitochondria to make energy.
If T4 → T3 conversion is blocked, you have high T4 in your blood but low T3 in your cells.
Your pituitary sees high T4. It thinks everything is fine. TSH stays normal.
But your cells are starving for T3. You feel hypothyroid even though your labs look good.
This is exactly what PUFAs do—they block T3 from entering cells.
What You Actually Need to Test
Free T3. This is active thyroid hormone. It should be in the upper half of the reference range. If it's low-normal or below, you're functionally hypothyroid regardless of TSH.
Free T4. This is the storage form. Check if your body is making enough raw material for conversion.
Reverse T3. This is inactive T3. Your body makes it when stressed or when conversion is impaired. High Reverse T3 blocks Free T3 from working.
TSH. Still useful. But don't rely on it alone. It's one piece of data, not the whole picture.
What the Numbers Mean
TSH:
- Below 0.5: Possibly hyperthyroid or overmedicated
- 0.5-2.0: Optimal for most people
- 2.0-4.0: Functional hypothyroidism likely (despite being "normal")
- Above 4.0: Clinical hypothyroidism
Free T3:
- Bottom half of range: Low cellular thyroid function
- Top half of range: Optimal
- Above range: Hyperthyroid or overmedicated
Free T4:
- Bottom third: Not making enough T4
- Middle to top: Adequate production
- Above range: Conversion problem or overmedication
Reverse T3:
- Low: Good
- High with low Free T3: Conversion block (stress, inflammation, PUFAs)
What Your Body Tells You (More Reliable Than Labs)
Temperature. Wake up. Measure under your tongue before getting up. 97.8°F to 98.6°F is optimal. Below 97.8°F consistently means low thyroid function at the cellular level. Full temperature tracking guide here.
Pulse. 75-85 bpm at rest is healthy. Below 70 usually correlates with low metabolism.
Symptoms:
- Cold hands and feet
- Low energy, especially afternoon crashes
- Weight gain despite same food intake
- Hair thinning or loss
- Dry skin
- Brain fog
- Constipation
- Heavy or irregular periods (women)
If you have these symptoms with "normal" TSH, your thyroid function is impaired at the cellular level.
What You Do
Request a full thyroid panel. Don't accept TSH-only testing. Ask for Free T3, Free T4, and Reverse T3.
Track your temperature and pulse daily. This gives you real-time cellular data. More useful than labs.
Eliminate seed oils. They block T3 from entering cells. Switch to saturated fats.
Eat enough carbohydrates. Your body needs glucose to convert T4 to T3. Low-carb diets suppress thyroid function in many people.
Reduce stress. Chronic cortisol increases Reverse T3 and blocks T3 receptors.
If you're on thyroid medication: Most prescriptions are T4-only (levothyroxine). If your Free T3 is still low, ask your doctor about adding T3 (liothyronine) or switching to NDT (natural desiccated thyroid).
Track your temperature. If it climbs toward 98°F and your energy improves, you're on the right track. If nothing changes after 4-6 weeks of PUFA elimination and adequate carbs, work with a functional medicine doctor who understands thyroid optimization.
FAQ
Q: Can I have hypothyroidism with normal TSH? A: Yes. This is called functional or subclinical hypothyroidism. Your TSH is in range but your Free T3 is low. You feel hypothyroid because your cells aren't getting enough active hormone.
Q: Should I ask my doctor for T3 medication? A: If your Free T3 is low and you have symptoms despite normal TSH, it's worth discussing. Some doctors are open to it. Others follow TSH-only protocols. You might need a functional medicine doctor.
Q: What if my doctor won't order a full panel? A: Order your own labs. Companies like Ulta Lab Tests or Quest Direct let you order thyroid panels without a doctor. Then bring results to your doctor or find one who will work with you.
Q: How often should I retest? A: Every 6-8 weeks if you're making changes (diet, medication). Once optimized, every 6-12 months for maintenance.
This isn't medical advice. I'm not your doctor. Work with a professional for thyroid management.
Want to optimize thyroid function naturally?
The SugarSaint course includes complete protocols for supporting thyroid health through diet, tracking body signals, and understanding your labs.
Not sure where to start?