- For most healthy non-pregnant adults, a normal TSH level falls between about 0.4 and 4.0 mIU/L, the standard reference range used by US laboratories.
- TSH reference ranges drift upward with age, so a value near 6.0 mIU/L can be normal for someone over 80 but high for a young adult.
- Newborns have very high TSH right after birth (up to 70 mIU/L in the first day) and pregnancy lowers the upper limit to roughly 4.0 mIU/L in the first trimester.
Part of our Thyroid Panel guide.
What is a normal TSH level?
For most healthy, non-pregnant adults, a normal thyroid-stimulating hormone (TSH) level is roughly 0.4 to 4.0 mIU/L, the reference interval reported by most US laboratories (StatPearls, NCBI). Some labs widen this to 0.4 to 4.5 mIU/L depending on the assay they use.
TSH is made by the pituitary gland, and it works like a thermostat for your thyroid. When thyroid hormone runs low, the pituitary pushes TSH up to demand more. When thyroid hormone is plentiful, TSH falls. That inverse relationship is why a high TSH usually signals an underactive thyroid (hypothyroidism), while a low TSH points to an overactive thyroid (hyperthyroidism). The number on its own is only part of the picture; clinicians read it alongside free T4 and your symptoms before drawing conclusions.
Want to check TSH yourself?
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TSH normal range by age
TSH reference ranges shift across the lifespan, and the upper limit tends to climb as people get older. Newborns run extremely high TSH at birth, children settle into wider intervals, and adults over 70 can be normal at values that would look elevated in a 30-year-old. The table below collects age-specific reference values from published medical sources.
| Age group | Approximate TSH range (mIU/L) | Note |
|---|---|---|
| Newborn (first 24 to 48 hours) | up to ~70 | Physiologic TSH surge after birth |
| Newborn (after day 3) | less than ~10 | Drops rapidly within days |
| Children (ages 1 to 6) | ~1.0 to 8.5 | Age-specific pediatric cutoffs |
| Children (ages 6 to 12) | ~1.0 to 7.0 | Narrows toward adult range |
| Adults (general) | 0.4 to 4.0 | Standard US lab reference |
| Older adults (ages 65 to 70) | ~0.65 to 5.5 | Upper limit rises with age |
| Older adults (ages 71 to 80) | ~0.85 to 5.9 | Mild elevation often benign |
| Older adults (over 80) | ~0.8 to 6.7 | Highest normal ceiling |
| Pregnancy (first trimester) | ~0.1 to 4.0 | Upper limit lowered by ATA |
Pediatric and newborn figures come from StatPearls (NCBI); the age-stratified older-adult intervals come from population studies indexed in PMC. Always read your own lab report, because the range printed next to your result is the one your lab validated for its assay.
How does sex change the range?
Sex has a smaller effect on TSH than age does, and most labs publish a single adult reference range of roughly 0.4 to 4.0 mIU/L for both men and women (StatPearls, NCBI). Where sex matters most is during the reproductive years, because pregnancy dramatically reshapes a woman’s range.
Women are also several times more likely than men to develop thyroid disease over a lifetime, and thyroid problems often surface around pregnancy, the postpartum window, and menopause. That is a difference in risk, not in the number that counts as normal on a routine panel. If you are pregnant or planning to conceive, the standard adult cutoff no longer applies and trimester-specific targets take over (see the next section). For non-pregnant adults, your clinician interprets the same range regardless of sex, weighting your symptoms and any family history of thyroid disease alongside the lab value.
What makes TSH rise or fall with age?
TSH tends to rise gradually with age, which is why the upper end of normal climbs into the 5 to 7 mIU/L territory in people over 70 (PMC). The French Endocrine Society has even suggested a rough rule of thumb of dividing a patient’s age by 10 to estimate the upper TSH limit when screening older adults.
Several forces move the number:
- Aging: The pituitary-thyroid set point shifts slightly upward, so mildly higher TSH can be a normal feature of older age rather than a disease.
- Pregnancy: The hormone hCG mimics TSH and stimulates the thyroid directly, which suppresses TSH and lowers the upper limit, especially in the first trimester (Endocrine Society).
- Medications: Levothyroxine, steroids, biotin supplements, lithium, and amiodarone can all push TSH up or down or interfere with the assay.
- Acute illness: Serious illness can temporarily distort thyroid tests, so clinicians often repeat the test once you recover.
When is an out-of-range result a concern?
A single out-of-range TSH is rarely an emergency, and clinicians usually confirm it with a repeat test plus a free T4 before acting. A TSH between about 4.5 and 10 mIU/L with normal free T4 is called subclinical hypothyroidism, and in many older adults it does not need treatment if there are no symptoms (Cleveland Clinic Journal of Medicine).
What clinicians watch for:
- High TSH (over 10 mIU/L): More likely to represent true hypothyroidism and is more often treated, especially with symptoms like fatigue, weight gain, cold intolerance, or constipation.
- Low or undetectable TSH: Suggests an overactive thyroid; symptoms can include palpitations, weight loss, tremor, and anxiety.
- Pregnancy: A TSH above the trimester-specific cutoff is taken more seriously because of effects on the developing baby.
- On treatment: People taking thyroid hormone are often targeted to roughly 0.5 to 3.0 mIU/L.
Context decides everything here. The same value can be reassuring in one person and worth following in another, which is why your result belongs in a conversation with your clinician rather than a chart alone.
Frequently asked questions
What is a dangerously high TSH level?
There is no single “danger” number, but a TSH above 10 mIU/L is more likely to reflect true hypothyroidism and is more often treated. Very high values, sometimes above 50 to 100 mIU/L, point to significant thyroid underactivity and warrant prompt medical evaluation.
Is a TSH of 5 normal for an older adult?
Often yes. The upper end of normal rises with age, reaching roughly 5.5 to 6.7 mIU/L in adults over 70 (PMC). A TSH of 5 with normal free T4 and no symptoms is frequently considered acceptable in an older person and may not need treatment.
What is the normal TSH range during pregnancy?
In the first trimester the American Thyroid Association uses an upper limit near 4.0 mIU/L, with trimester-specific targets of roughly 0.1 to 4.0 (first), 0.2 to 3.0 (second), and 0.3 to 3.5 mIU/L (third). Your obstetric provider sets the exact target.
Can TSH levels change throughout the day?
Yes. TSH follows a daily rhythm, peaking overnight and dipping in the afternoon, so values can vary by time of day. For consistency, many clinicians draw the test in the morning and repeat borderline results before making any decisions.
Should I worry about a slightly high TSH?
A mildly high TSH with normal free T4 (subclinical hypothyroidism) is common and often does not need treatment, particularly in older adults without symptoms. Clinicians usually repeat the test in a few weeks rather than starting medication immediately. Discuss your result with your provider.
Sources
- StatPearls (NCBI), Thyroid-Stimulating Hormone
- StatPearls (NCBI), Pediatric Hypothyroidism
- PMC, Reference intervals for thyroid hormones in the elderly population
- PMC, Age-specific serum thyrotropin reference range in the elderly
- Endocrine Society, TSH and FT4 Reference Intervals in Pregnancy
- Cleveland Clinic Journal of Medicine, Subclinical hypothyroidism: When to treat
This article is for general educational purposes and is not medical advice. It cannot diagnose or treat you and does not replace your clinician. Always discuss your lab results and any health decisions with a qualified healthcare professional.
