High TSH: What It Means and What to Do Next
A high TSH level (above 4.0 mIU/L) means your thyroid is underactive — hypothyroidism. Your pituitary produces extra TSH trying to stimulate more thyroid hormone. This is the most common thyroid abnormality and is treatable with levothyroxine medication.
What Causes High TSH?
Hypothyroidism
The most common cause. Your thyroid gland isn't producing enough thyroid hormone, so your pituitary raises TSH to compensate.
Hashimoto's Thyroiditis
An autoimmune condition where your immune system attacks your thyroid, gradually destroying its ability to produce hormone.
Iodine Deficiency
Iodine is essential for thyroid hormone production. Deficiency is rare in the US but common globally.
Thyroid Surgery or Radiation
Previous treatment that removed or damaged thyroid tissue reduces hormone production.
Medication Effects
Lithium, amiodarone, and some other medications can impair thyroid function and raise TSH.
Associated Symptoms
What to Do Next
1. Retest to confirm
A single abnormal result should be confirmed with a repeat test. Temporary factors like stress, illness, or medications can affect results.
2. Related tests to consider
3. When to see a doctor
If your TSH is significantly abnormal, if you have severe symptoms, or if repeated results confirm the abnormality, consult a healthcare professional for appropriate evaluation and treatment.
Related Conditions
Frequently Asked Questions
Related Articles
Which thyroid tests you actually need to monitor Hashimoto's and track antibody levels.
How to get TSH, Free T4, and Free T3 tested affordably without insurance coverage.
Why Free T3 matters for thyroid health and when to add it to your panel.
This page is for informational purposes only and does not constitute medical advice. Consult a healthcare provider for interpretation of your results.
Content reviewed for accuracy by the JustLabs editorial team.