Thyroid Test (TSH, T3, T4): Normal Range, Symptoms and When to Get Tested

Thyroid problems are very common in India, especially in women. Studies suggest about 1 in 10 Indian adults has hypothyroidism, and many are undiagnosed. A simple blood test can find it.

What does the thyroid do?

The thyroid is a butterfly-shaped gland in the neck. Its hormones, T3 and T4, control how fast your body uses energy, affecting weight, heart rate, mood, periods and more. The brain controls the thyroid using TSH (thyroid stimulating hormone).

Thyroid test normal range

*Ranges vary between laboratories. Always read your result against the range printed on your report.

How to read your result

• High TSH, low T4 → underactive thyroid (hypothyroidism)
• High TSH, normal T4 → subclinical hypothyroidism, which may only need monitoring
• Low TSH, high T3/T4 → overactive thyroid (hyperthyroidism)

Symptoms of an underactive thyroid

• Tiredness and sleepiness
• Weight gain
• Feeling cold
• Dry skin and hair fall
• Constipation
• Heavy or irregular periods, difficulty conceiving
• Low mood

Symptoms of an overactive thyroid

• Weight loss despite a good appetite
• Palpitations and anxiety
• Feeling hot and sweaty
• Tremor of the hands
• Bulging eyes (in Graves disease)

Thyroid in pregnancy

Thyroid hormone is essential for the baby's brain development. TSH targets are lower in pregnancy, and women already on thyroid tablets usually need a higher dose. Get a TSH test when planning pregnancy or as soon as you know you are pregnant, and follow your gynaecologist's advice.

Who should get tested?

• Anyone with the symptoms above
• Women planning pregnancy or who are pregnant
• People with a family history of thyroid disease
• People with diabetes, PCOS or high cholesterol

How to prepare for the test

No fasting is usually needed. If you already take a thyroid tablet, give the sample before that day's dose, ideally at the same time of day as previous tests.

Treatment

Hypothyroidism is treated with a daily levothyroxine tablet (brands include Thyronorm and Thyrox), taken on an empty stomach 30–60 minutes before breakfast or tea, and kept 4 hours apart from calcium and iron supplements. TSH is rechecked after 6–8 weeks to adjust the dose. Hyperthyroidism is treated with anti-thyroid medicines, radioactive iodine or surgery.

When to see a doctor

See a general physician or endocrinologist if your TSH is outside the range or you have symptoms.

What causes thyroid problems in India?

• Autoimmune thyroiditis (Hashimoto's), where the immune system attacks the thyroid, is the most common cause of hypothyroidism.
• Iodine deficiency was once widespread; iodised salt has greatly reduced it, but it still occurs in some areas.
• After pregnancy, some women develop temporary thyroid inflammation.
• Graves disease is the most common cause of an overactive thyroid.
• Some medicines, neck radiation and thyroid surgery can also affect thyroid function.

Thyroid antibodies (anti-TPO)

If your TSH is borderline, your doctor may order an anti-TPO antibody test. A positive result suggests autoimmune thyroid disease and a higher chance of developing hypothyroidism over time, which helps decide whether to start treatment.

Thyroid and weight

An underactive thyroid can add a few kilos, mostly due to fluid retention and a slower metabolism. Treating it helps, but it rarely explains large weight gain on its own. Diet, activity and sleep still matter.

Thyroid and diet

• Use iodised salt, but you do not need extra iodine supplements unless advised.
• Soy, cabbage and cauliflower are fine in normal amounts when cooked.
• Take your thyroid tablet on an empty stomach and keep tea, coffee, milk, calcium and iron away from it by the advised gap.

How often should TSH be checked?

After starting or changing the dose, TSH is usually rechecked in 6–8 weeks. Once stable, most people need a check every 6–12 months, and more often in pregnancy.

Myths and facts

• Myth: "Thyroid tablets cause weight loss." Fact: The right dose only brings hormone levels to normal.
• Myth: "I can stop the tablet once I feel better." Fact: Feeling better usually means the dose is right; stopping brings symptoms back.
• Myth: "Thyroid problems stop you from getting pregnant." Fact: Well-controlled thyroid disease is compatible with a healthy pregnancy.