🚨 Quick Navigation for Readers in Distress
- If your doctor only tests TSH
- If you need Free T3 and Free T4
- If you took medication before testing
- If you’re curious about Reverse T3
- Read Part 1: T3 deficiency basics
- Read Part 3: Medication access abroad
Why This Post Exists
If you have been told “your labs are fine,” yet your body disagrees, you already know the problem. Many patients do everything right. They take medication, show up for thyroid blood tests, and trust the process. Still, they feel unwell. Thyroid blood tests are often interpreted for speed, not patterns.
⚠️ Important Medical Disclaimer
This article shares lived experience and patient-led education. It does not replace medical advice, diagnosis, or treatment. Thyroid disease is complex and individual. Always consult a qualified clinician before changing medication, dose, or timing.
TSH-Only Thyroid Blood Tests: Why They Fall Short
Thyroid Stimulating Hormone, or TSH, is a pituitary signal, not thyroid hormone itself. In an unmedicated person, it can be a useful starting point. However, once you take thyroid hormone, TSH becomes a less reliable narrator. It can look “perfect” even when tissues are underpowered.
Medication changes the feedback loop between the brain and the thyroid. When we supplement the body with thyroid hormone, the pituitary gland no longer needs to send strong signals to the thyroid to produce more. As a result, TSH levels often fall. This is a normal and expected response to thyroid hormone replacement, not an automatic sign of overmedication.
For this reason, a “normal” TSH on levothyroxine does not guarantee that enough active hormone is reaching the cells. Equally, a low or suppressed TSH in someone taking thyroid hormone does not automatically mean the dose is too high. It can simply reflect that the body is receiving hormone from an external source, so the demand signal decreases.
However, many clinicians are trained to respond to a low TSH by reducing medication, often without considering symptoms or measuring Free T3 and Free T4 as part of a comprehensive panel of thyroid blood tests. When this happens, patients can become under-medicated. Over time, symptoms return, energy drops, and the body again signals distress. Eventually, TSH may rise once more, restarting the cycle.
This is why TSH alone is an unreliable guide in people who are already on thyroid hormone replacement. If symptoms persist, or if dose changes are being made based solely on TSH, it is reasonable and appropriate to look deeper and assess how much active hormone is actually available at the cellular level.
Free T3 and Free T4: What Your Cells Can Actually Use
Most laboratories offer total T3 and total T4 blood tests, which are significantly cheaper than testing Free T3 and Free T4. In countries like New Zealand, where blood tests are often fully or partially funded, these cheaper tests frequently become the default. In some cases, only TSH is ordered. As outlined earlier, this provides a very limited snapshot and is insufficient for accurately titrating thyroid hormone replacement.
Total T3 and T4 measure both hormone that is bound to carrier proteins and hormone that is biologically available. The bound portion, however, cannot be used by cells. By contrast, Free T3 and Free T4 measure the unbound hormone that tissues can actually access, making them far more clinically meaningful when symptoms persist despite treatment.
Free T4 reflects circulating hormone from both thyroid output and medication. Free T3 reflects how much of that hormone has been converted into its active form. When interpreted together with TSH, these tests offer a far clearer picture of thyroid function than TSH alone.
Why Free T3 and Free T4 Are Often Overlooked
Sometimes it comes down to cost. Sometimes it is habit. Sometimes it is adherence to guidelines designed around population averages rather than individual physiology. But if you are symptomatic, you are not a spreadsheet. You are a human body with a history, a stress load, and a unique genetic makeup. In those circumstances, deeper testing is not excessive. It is appropriate.
Medication Timing Before Blood Tests: The Detail That Changes Everything
If you take levothyroxine right before testing, blood can reflect the tablet rather than baseline. That is especially true for T4 measures, and it can distort interpretation. The test may capture what is floating in blood, not what is being used in tissues.
Many patients test early in the morning and take medication after the blood draw, unless instructed otherwise. Also, write down the time of your last dose and share it. This detail prevents misunderstandings.
What doctors often forget to ask
I was rarely asked when I had taken my last thyroid dose before a blood test. Instead, results were often relayed back to me in a single sentence: “Everything looks normal.” What that usually meant was that nothing had triggered an asterisk on the lab report.
Many clinicians scan large volumes of results each day. If a value sits within the laboratory reference range, no asterisk appears and no further action is taken. There is rarely a pause to consider trends over time, whether a result is sitting right at the bottom or top of the range, or how that compares to previous tests. Subtle but clinically meaningful shifts are easily missed when the only question being asked is whether a number has crossed an arbitrary line.
In New Zealand, following up on blood test results typically required booking a separate appointment. That meant wait times, additional cost, and often repeating the same conversation from scratch. The process was frustrating and laborious, and over time it became exhausting to continually advocate for myself just to have results looked at in context rather than in isolation.
Eventually, I stopped relying on verbal summaries. I always request a copy of my laboratory reports, review the numbers myself, compare trends across time, and prepare questions before the next appointment. This approach has been born out of necessity, not defiance. The fact that I know my own body better than anyone else, and can feel when I am well and when something is off, has too often seemed immaterial within a system that prioritises reference ranges over lived experience.
This is not about distrusting medicine. It is about recognising that numbers do not exist in a vacuum, and that effective care requires context, pattern recognition, and listening to the person those numbers belong to. All of which becomes increasingly challenging in a system that allocates 15 minutes for a doctor’s appointment.
Reverse T3 Testing: The Missing Puzzle Piece for Some
Reverse T3 is an inactive form that can compete with active T3 at the cellular level. When it is elevated, people may feel hypothyroid even with decent-looking T4 results. It is not the answer for everyone. Yet for some, it explains why T4-only treatment fails.
In New Zealand, Reverse T3 testing is not routinely available. In my case, the sample had to be sent to Australia. It required careful logistics and it was very costly. My Reverse T3 came back normal, but many people find it clarifies confusing symptoms.
Why Accurate Testing Matters Before Changing Medication
For people considering T3-containing treatments, including Whole Thyroid (also known as Armour or desiccated porcine thyroid), accurate blood testing becomes even more important.
Access challenges, particularly for those living abroad, can push patients to seek alternative supply routes. However, without understanding Free T3, Free T4, and overall trends, changing or sourcing medication without guidance can increase risk.
Even when emergency options exist, laboratory data and clinical evaluation remain essential. Knowing what your body needs should always come before deciding how to obtain it.
How to Advocate Without Burning Out
Keep it simple. Bring a one-page symptom summary. Ask for TSH, Free T4, and Free T3 blood tests to be ordered. If you want Reverse T3, ask what the process is and what it costs. If a test is refused, ask why, and request that the refusal be noted.
If a conversation turns into dismissal, regroup. You can change clinicians or seek an endocrinologist. You can look for integrative care, even if it is shrinking in places like New Zealand. If you live abroad, plan ahead.
Where This Connects to Living Abroad
For readers in Nicaragua and Central & South America, obtaining comprehensive thyroid blood tests is only half the battle. Medication access is the other half. If you cannot obtain T3 or Armour locally, lab strategy becomes even more important. It reduces risk when you must use alternatives.
In Part 3, I explain medication access abroad and the pathway that worked for me, including compounding by a pharmacy in Costa Rica. You can also explore this Costa Rica integrative medicine directory for connections that understand T3.
When doctors dismiss symptoms, self-trust gets shaken. That is the quiet harm. If you are told you are “overthinking,” pause. Bring data. Bring timelines. Then bring support. A friend in the room can help. Written questions help too. You deserve respectful care.
Take the Next Step
If you are running low on medication or you feel stuck, do not wait until you crash. Send us your email using the form below and we’ll email you our Emergency Thyroid Checklist PDF.
