Understanding normal TSH levels helps you interpret your blood test results and know when to seek treatment. While the standard adult range is 0.4–4.0 mIU/L, your ideal level can vary by age, sex, and life stage.
Standard Normal TSH Range for Adults
Most laboratories define a normal TSH level for adults as 0.4 to 4.0 mIU/L. Some use an upper limit of 5.0 mIU/L. Levels within this range generally indicate that the thyroid is producing adequate hormones.
Normal TSH Levels by Age
| Age Group | Typical TSH Range (mIU/L) |
|---|---|
| Newborns | 1.0 – 39.0 |
| Children | 0.7 – 6.4 |
| Adults (18–60) | 0.4 – 4.0 |
| Older adults (70+) | 0.4 – 5.5 |
Normal TSH Levels for Women
Women often have slightly different TSH patterns due to hormonal cycles. During pregnancy, the normal range drops significantly:
- First trimester: 0.1 – 2.5
- Second trimester: 0.2 – 3.0
- Third trimester: 0.3 – 3.0
Normal TSH Levels for Men
Men typically fall within the standard adult range. However, low testosterone or metabolic syndrome can sometimes be associated with slightly elevated TSH.
Borderline TSH: When to Worry
A TSH between 0.1–0.3 or 4.1–10.0 is considered borderline. Your doctor may recommend repeat testing, symptom evaluation, or a full thyroid panel before starting treatment.
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