Thyroid Tests Explained: TSH, T3, T4 & What Your Results Mean

Feeling unusually tired, gaining or losing weight without reason, or just not feeling like yourself lately? You may want to consider getting thyroid tests done. Your thyroid is a small gland with a big job. It controls your metabolism, energy, mood, and more. When it is out of balance, it can affect almost every part of your body, often without you even realising it. ¹

This is where thyroid blood tests, such as TSH, T3, and T4, come into the picture. But what exactly do they measure? And how do you know if your results are normal? If you are wondering the same, this post is for you. It will take you through everything you need to know about thyroid tests: what they are, when to get them, their results, and symptoms to watch for.

Whether you are concerned about hypothyroidism, hyperthyroidism, or just want to stay proactive about your health, this blog will help you make informed decisions.

What Is The Thyroid and Why Does It Matter?

Alt text: Woman pointing towards her neck to highlight the thyroid gland

The thyroid is a butterfly-shaped gland located in the front of your neck. It produces hormones that regulate your body’s metabolism. These hormones also impact your weight, heart rate, mood, and more.

A healthy thyroid helps your body function smoothly. When it underperforms or overproduces hormones, it can lead to disorders such as hypothyroidism or hyperthyroidism. That is why thyroid tests are so important. Let us learn more about them below. 

Overview of Common Thyroid Tests

To check how well your thyroid is working, your doctor may recommend a thyroid function test. This usually includes three key thyroid hormone tests: TSH, T3, and T4. ²

TSH (Thyroid Stimulating Hormone)

The pituitary gland produces TSH. It signals your thyroid about how much T3 and T4 it needs to make. A TSH test is often the first test done to assess thyroid function. High TSH levels may indicate an underactive thyroid, known as hypothyroidism, while low levels may signal hyperthyroidism, an overactive thyroid. ³

T4 (Thyroxine)

T4 is the most abundant hormone produced by your thyroid. It circulates in your bloodstream and gets converted into T3, the active form your body uses. When doctors check thyroid function, they often measure Free T4, which is the portion of T4 that is not bound to proteins and is available for your body to use. Low Free T4 levels typically point to hypothyroidism, while high levels may suggest hyperthyroidism. 

However, total T4 levels can sometimes be misleading. This is because most of the T4 in your blood is attached to proteins that store it for later use. Only a small amount is free and active. Certain conditions, like pregnancy or taking birth control pills, can raise these binding proteins. On the other hand, illnesses or medications like steroids can lower them. These shifts can change your total T4 levels without truly reflecting your thyroid health. Due to this reason, free T4 is considered more accurate and is often the test your doctor will rely on for a clearer picture of how your thyroid is functioning. ⁴

T3 (Triiodothyronine)

T3 is the active thyroid hormone that helps manage key functions, such as your metabolism, body temperature, and heart rate. Most of it comes from the conversion of T4 into T3 inside your body.

In some cases, your T4 levels might look normal even if something’s off. That is where a T3 test can help. If your doctor suspects hyperthyroidism but your T4 results are within range, they may check your T3 levels. ⁵

Apart from these three tests, your doctor may also recommend a thyroid antibodies test. It measures the thyroid antibodies in your blood to diagnose autoimmune thyroid disorders.

Each of these tests helps assess how well your thyroid is working. But how do you know when to get tested? Check out the next section to explore some of the most common symptoms of a thyroid imbalance.

Symptoms of Thyroid Imbalance

A thyroid that is not functioning properly can lead to a wide range of symptoms, often mistaken for other health issues. Here is what to watch out for: ^{6, 7, 8, 9}

Common Symptoms of Hypothyroidism (Underactive Thyroid)

• Unexplained weight gain
• Constant tiredness
• Feeling unusually cold
• Dry or rough skin
• Muscle aches or cramps
• Joint pain or stiffness
• Hair thinning or hair loss
• Puffy face
• Heavy or irregular periods
• Low mood or depression
• Slower than normal heart rate
• Fertility issues
• Constipation
• Less sweating than usual
• Swelling at the front of the neck (goitre)

Common Symptoms of Hyperthyroidism (Overactive Thyroid)

• Sudden or unexplained weight loss
• Mood changes
• Irregular heartbeat
• Feeling irritable or restless
• Tiredness despite enough sleep
• Shaky hands
• Increased sweating
• Difficulty sleeping
• Heat sensitivity
• Muscle weakness
• More frequent bowel movements
• Goitre 

If any of these symptoms sound familiar, it might be time to check in on your thyroid health. But symptoms are not the only reason to get tested. Let us explore when else a thyroid test might be a good idea.

When and Why You Should Take a Thyroid Test

You should consider a thyroid blood test if you: ¹⁰

• Have a family history of thyroid disease
• Are you pregnant or planning to conceive
• Are taking medications that can affect thyroid function, like lithium or amiodarone
• Are a woman over the age of 35.

In many cases, doctors include thyroid tests as part of routine health screenings. But do you know how to understand T3, T4, and TSH results? The next section will help you find out.

Understanding Your Results – What Do They Mean?

Here is a simple breakdown of what different results might indicate: ¹¹

• A high TSH test result usually indicates hypothyroidism.
• Low TSH may signal hyperthyroidism.
• Low T3-T4 test results may indicate hypothyroidism.
• High free T3 and T4 levels may suggest hyperthyroidism.

It is important to note that it is just a general idea. For accurate interpretation of the results, always consult a doctor. Depending on your symptoms, they may also recommend a thyroid antibodies test or an ultrasound for detailed diagnosis.

Now that you know everything you need to know about hypothyroidism and hyperthyroidism tests, let us walk you through how to prepare for them.

How to Prepare for the Thyroid Test?

Thyroid tests are usually simple blood tests and do not require extensive preparation. However, the American Thyroid Association suggests avoiding biotin supplements for at least 2 days before the test. This is because it may lead to falsely high T4 and T3 and low TSH levels. 12

Apart from this, keep the following things in mind:

• Always inform your doctor about any supplements or prescription medicines you take.
• Take your regular medications unless advised otherwise.
• You may eat and drink normally unless advised otherwise.
• Stay relaxed and rested before the test.

Once you know how to get ready for the test, the next thing you might be wondering is: how much does it cost? Keep reading to find out the typical prices of thyroid tests in India.

Cost of Thyroid Tests in India (TSH, T3, T4)

The TSH test may cost around ₹300-400 in India. If you opt for a Thyroid Profile (T3, T4, and TSH) test, the cost may range from ₹500 to ₹850. However, the exact price may vary depending on the location and provider:

You can also choose at-home sample collection through most major diagnostic labs, such as Lifecell. This includes no extra cost and is super convenient, especially if you are feeling unwell or managing a busy schedule. Book Your Thyroid Test today with Lifecell Diagnostics and take the first step toward better thyroid health.

The Wrap Up

Thyroid tests, including TSH, T3, and T4, are key to understanding your body’s metabolism, energy levels, and overall well-being. Whether you are screening for an overactive thyroid or need a hypothyroidism test to investigate symptoms like fatigue and weight gain, testing early can help you get the right treatment at the right time. These tests can also be part of your routine health check-up, especially if you have a family history or other risk factors.

For a complete and convenient solution, try the Ayushman Total Package by Lifecell Diagnostics. It includes essential thyroid tests along with other important health markers. What’s more? You also get the added benefit of at-home sample collection at no extra cost.

FAQs

What are Normal TSH, T3, and T4 Levels?

The normal TSH, T3, and T4 levels are: ¹³

• TSH: 0.35–4.94 IU/L
• Total T3: 0.57–1.59 ng/mL
• Total T4: 4.87–11.72 μg/dL
• Free T3: 1.71–3.71 pg/mL
• Free T4: 0.7–1.48 ng/dL.

Here, it is important to note that reference ranges may vary slightly between labs. So, it is a good idea to review the specific values listed in your lab report and discuss them with your doctor.

Which is Most Important, T3, T4 or TSH?

When it comes to thyroid tests, TSH is usually the most important starting point. It is the first to show changes when your thyroid is out of balance, making it a reliable indicator of thyroid function. T4 is typically checked next, followed by T3 if needed, especially in suspected cases of hyperthyroidism. ¹⁴

Is Fasting Required For a T3, T4, and TSH test?

No, fasting is usually not required for a T3, T4, and TSH test. You can eat and drink as usual before the test. However, if you are getting other blood work done along with thyroid tests, your doctor may ask you to fast. Always follow their specific instructions.