TSH Levels Chart by Age: Normal Ranges and Meaning

Normal TSH levels depend on age, laboratory method, pregnancy status, medications, and individual health factors. In many adults, the laboratory reference range is approximately 0.4 to 4.0 mIU/L, but children may have higher limits, and TSH can naturally rise somewhat in older adults.

A TSH levels chart by age can provide useful context, but it should not replace the reference range printed on your laboratory report. Doctors usually interpret TSH together with free T4, symptoms, medications, previous results, and thyroid history.

Table of Contents

TSH Levels Chart by Age

The following chart uses current age-specific reference intervals published by Mayo Clinic Laboratories.

Age	Example Normal TSH Range
Birth to 5 days	0.7–15.2 mIU/L
6 days to 2 months	0.7–11.0 mIU/L
3–11 months	0.7–8.4 mIU/L
1–5 years	0.7–6.0 mIU/L
6–10 years	0.6–4.8 mIU/L
11–19 years	0.5–4.3 mIU/L
20 years and older	0.3–4.2 mIU/L

These are example laboratory reference intervals, not universal diagnostic thresholds. Another laboratory may use slightly different lower and upper limits because testing equipment, methods, and reference populations vary. Always compare your result with the range shown beside it on your own report.

Important Notes About the Chart

mIU/L and µIU/mL are numerically equivalent. A TSH of 3.0 mIU/L is the same numerical concentration as 3.0 µIU/mL.
Newborn and pediatric ranges are different from adult ranges.
Pregnancy requires pregnancy-specific interpretation.
Older adults may have a mildly higher TSH without having an underactive thyroid.
People taking thyroid medicine may have an individualized target rather than the general population range.
A reference interval does not confirm or rule out disease by itself.

What Is TSH?

TSH stands for thyroid-stimulating hormone, also called thyrotropin. It is produced by the pituitary gland, a small gland at the base of the brain.

TSH acts as a signal telling the thyroid gland how much thyroid hormone to produce. The thyroid mainly releases thyroxine, or T4, which is converted into the more active hormone T3 in body tissues.

The relationship works like a thermostat:

When thyroid hormone levels are low, the pituitary usually releases more TSH.
When thyroid hormone levels are high, the pituitary usually releases less TSH.

This is why a high TSH often points toward an underactive thyroid, while a low TSH often points toward an overactive thyroid. However, exceptions can occur, particularly with pituitary disorders, severe illness, pregnancy, medications, and laboratory interference.

The American Thyroid Association’s thyroid function testing guide explains that TSH is generally the best initial blood test for evaluating thyroid function.

What Is a Normal TSH Level for Adults?

Many laboratories use an adult TSH reference range close to:

0.4 to 4.0 mIU/L

However, some laboratories use values such as 0.3 to 4.2 mIU/L, 0.4 to 4.5 mIU/L, or another similar interval.

A result within the laboratory range usually suggests that the thyroid is functioning normally when the pituitary gland is healthy. However, a normal TSH does not explain every thyroid-related symptom, and unusual combinations of TSH and free T4 may require further investigation.

The following general interpretation is commonly used for adults who are not pregnant and are not taking medicines intended to suppress TSH:

TSH Result	General Interpretation
Below the laboratory range	Low TSH
Within the laboratory range	Usually considered normal
Slightly above the range	Mildly elevated TSH
Clearly above the range	More consistent with reduced thyroid function, depending on free T4

These categories do not determine whether treatment is necessary. Treatment decisions depend on factors such as free T4, symptoms, age, pregnancy plans, thyroid antibodies, heart health, and how persistent the abnormal result is.

How TSH Levels Change With Age

TSH Levels in Newborns

TSH can be much higher during the first days of life than it is later in childhood or adulthood. The value generally falls quickly after birth.

Newborn screening programs test babies for congenital hypothyroidism because thyroid hormone is important for normal growth and brain development. Screening thresholds and follow-up procedures may differ from the serum ranges used for older children.

An adult TSH range should never be used to interpret a newborn’s result.

TSH Levels in Infants and Children

Normal TSH upper limits gradually decrease through infancy and childhood. For example, Mayo Clinic Laboratories lists an upper limit of 11.0 mIU/L for babies ages 6 days to 2 months but 4.8 mIU/L for children ages 6 to 10 years.

Pediatric thyroid results should be compared with an age-specific range. Doctors may also consider:

Growth rate
Puberty and development
Free T4
Family history
Thyroid antibodies
Symptoms
Newborn screening history

TSH Levels in Teenagers

By adolescence, the normal range becomes closer to the adult range. Mayo Clinic Laboratories currently lists a TSH reference interval of 0.5 to 4.3 mIU/L for ages 11 to 19.

Symptoms such as fatigue, weight changes, mood changes, irregular menstrual periods, difficulty concentrating, or slowed growth can have many causes. A TSH result should therefore be evaluated with other findings rather than interpreted alone.

TSH Levels in Younger and Middle-Aged Adults

Most adults younger than 50 or 60 are evaluated using the laboratory’s standard adult range. In many laboratories, the upper limit is near 4.0 mIU/L.

An adult result slightly outside the range may be repeated before a diagnosis is made, particularly when free T4 is normal and the person has no significant symptoms. Temporary illness, medication changes, supplement interference, or normal biological variation may affect the result.

TSH Levels in Adults Over 50

TSH may begin to trend upward with age, even in people without clear thyroid disease.

A 2024 multicenter study based on approximately 7.6 million TSH tests found that the upper TSH reference limit began increasing around age 50 in women and age 60 in men. Applying age-specific intervals reduced the number of older adults classified as having hypothyroidism. (Jansen et al., 2024)

This does not mean an elevated result should be ignored. It means clinicians may consider age before labeling a mild elevation as thyroid disease.

TSH Levels in Adults Over 70

A mildly elevated TSH with a normal free T4 may be more common in older adults. Interpretation should consider:

Whether the result is new or stable
Free T4 level
Thyroid antibodies
Symptoms
Heart rhythm and cardiovascular history
Current medications
Frailty and other health conditions
Previous thyroid treatment

A 2025 study using US and Chinese population data found that the upper TSH percentile increased with age. Using age-, sex-, and race-specific intervals reclassified almost half of participants initially categorized as having subclinical hypothyroidism as being within an adjusted reference range. (Li et al., 2025)

TSH Levels in Adults Over 80

TSH may be higher after age 80 without an underlying thyroid disorder. The MedlinePlus TSH test guide specifically notes that older adults may have higher values despite having a healthy thyroid.

Recent longitudinal research published in 2026 found that most people had relatively stable thyroid function as they aged, with only a slight average increase in TSH. However, thyroid test results became more variable after approximately age 65. This supports looking at personal trends and repeat results instead of relying on one universal cutoff.

Does TSH Normally Increase With Age?

TSH often increases modestly with age, especially in older adulthood. Several large studies have found that the upper end of the TSH distribution is higher among older adults than among younger adults.

Possible explanations include changes in:

Pituitary-thyroid signaling
Thyroid hormone metabolism
Medication use
Chronic illness
Iodine exposure
Autoimmune thyroid disease
Individual thyroid set points

Age-related increases are usually modest. A markedly elevated TSH, a low free T4, significant symptoms, or steadily rising results still require medical evaluation.

What Does a High TSH Level Mean?

A high TSH usually means the pituitary gland is sending a stronger signal because the thyroid is not producing enough thyroid hormone.

Possible causes include:

Hashimoto’s thyroiditis
Primary hypothyroidism
Previous thyroid surgery
Radioactive iodine treatment
Certain medications
Too little thyroid hormone replacement
Missed levothyroxine doses
Reduced levothyroxine absorption
Recovery from a serious illness
Age-related changes
Laboratory interference

Common Symptoms Associated With Hypothyroidism

People with an underactive thyroid may experience:

Fatigue
Increased sensitivity to cold
Dry skin
Constipation
Unexplained weight gain
Muscle aches or weakness
Slower heart rate
Thinning hair
Heavy or irregular menstrual periods
Difficulty concentrating
Low mood
Puffiness around the face

These symptoms are not specific to thyroid disease. Some people with an elevated TSH have few or no symptoms, while people with similar symptoms may have normal thyroid results.

What Does a Low TSH Level Mean?

A low TSH usually means the pituitary is reducing its signal because thyroid hormone levels are high.

Possible causes include:

Graves’ disease
Overactive thyroid nodules
Thyroiditis
Excess thyroid hormone medication
Pregnancy-related hormonal changes
Certain medications
Serious non-thyroid illness
Laboratory interference
Pituitary or hypothalamic disease

Common Symptoms Associated With Hyperthyroidism

Possible symptoms include:

Rapid or irregular heartbeat
Unexplained weight loss
Shaky hands
Increased sweating
Heat intolerance
Anxiety or irritability
Muscle weakness
Frequent bowel movements
Difficulty sleeping
Neck swelling or goiter

Older adults may not develop the classic symptoms. They may instead experience fatigue, reduced appetite, weakness, heart rhythm changes, or social withdrawal.

How TSH and Free T4 Results Are Interpreted Together

TSH is most useful when interpreted with free T4. Free T4 measures the portion of circulating T4 that is not bound to proteins and is available to body tissues.

TSH	Free T4	Possible Meaning
High	Low	Primary hypothyroidism
High	Normal	Possible subclinical hypothyroidism
Low	High	Hyperthyroidism
Low	Normal	Possible subclinical hyperthyroidism
Low or inappropriately normal	Low	Possible pituitary or hypothalamic disorder
Normal	Normal	Thyroid function is usually normal

“Subclinical” means that TSH is outside the reference interval while free T4 remains within its normal range. It does not mean symptoms are imaginary or that the result should automatically be treated.

The appropriate next step may involve repeat testing, monitoring, thyroid antibody testing, medication review, or treatment depending on the full clinical situation. The American Thyroid Association confirms that an elevated TSH with low free T4 is typical of primary hypothyroidism, while a low TSH with elevated free T4 is typical of hyperthyroidism.

Can You Have Thyroid Disease With a Normal TSH?

It is possible, although uncommon in otherwise healthy people.

Examples include:

Pituitary or hypothalamic disease
Recent changes in thyroid medication
Early or fluctuating thyroid disease
Severe non-thyroid illness
Pregnancy
Laboratory interference
Unusual thyroid hormone resistance or transport disorders

A normal TSH is generally reassuring, but healthcare professionals may order free T4, T3, thyroid antibodies, or other tests when symptoms or medical history suggest that more evaluation is necessary.

Factors That Can Affect TSH Test Results

Time of Day

TSH follows a daily rhythm. Levels generally peak during the night and are lower during the daytime. The difference is usually not large enough to change routine interpretation, but testing at a similar time can make repeated measurements easier to compare.

Illness

Serious illness can temporarily lower or raise TSH even when the thyroid itself is healthy. Testing may need to be repeated after recovery when an unexpected result does not match the clinical picture.

Pregnancy

Pregnancy changes thyroid hormone production, binding proteins, iodine needs, and TSH levels. General adult ranges may not be appropriate.

Medications

Medicines that may affect thyroid function or test interpretation include:

Thyroid hormone replacement
Antithyroid medicines
Amiodarone
Lithium
Corticosteroids
Dopamine-related medicines
Some cancer treatments
Estrogen-containing medicines

Do not stop a prescription medicine before testing unless your healthcare professional tells you to do so.

Biotin Supplements

Biotin is commonly included in supplements marketed for hair, skin, or nails. It can interfere with some laboratory methods and may make TSH appear falsely low while making thyroid hormone levels appear falsely high.

The American Thyroid Association advises avoiding biotin for at least two days before thyroid testing, but the appropriate timing may depend on the dose and the laboratory method. Tell your healthcare professional and laboratory about every supplement you take.

Iodine Exposure

Too little or too much iodine can influence thyroid function. Iodine may be found in:

Iodized salt
Seaweed products
Some supplements
Certain medications
Iodine-containing imaging contrast

Do not start a high-dose iodine supplement to correct an abnormal TSH without medical guidance.

Thyroid Medication Timing and Absorption

Levothyroxine absorption may be affected by food, calcium, iron, antacids, and certain medications. Inconsistent dosing can cause TSH results to fluctuate.

Take thyroid medicine exactly as prescribed and tell your healthcare professional about missed doses or changes in your routine.

TSH Levels During Pregnancy

Pregnancy requires separate interpretation because TSH often falls during the first trimester as pregnancy hormones stimulate the thyroid.

The ideal approach is to use:

Trimester-specific ranges
Population-specific ranges
The laboratory’s pregnancy reference interval
An individualized target for anyone already taking thyroid medication

The American Thyroid Association released updated pregnancy and postpartum guidelines in June 2026. The guidance covers thyroid testing, hypothyroidism, hyperthyroidism, thyroid autoimmunity, iodine, thyroid nodules, and postpartum thyroid dysfunction. Pregnant readers should follow the target provided by their obstetrician or thyroid specialist rather than a general adult TSH chart. (2026 ATA pregnancy guideline announcement)

Contact a healthcare professional promptly if you are pregnant, planning pregnancy, or recently gave birth and have an abnormal TSH result or a history of thyroid disease.

Should an Abnormal TSH Test Be Repeated?

A repeat test may be appropriate when:

The elevation or suppression is mild
Free T4 is normal
You recently had a serious illness
You recently started or changed medication
You take biotin or another interfering supplement
The result does not match your symptoms
A laboratory error or interference is suspected
The result is unexpected compared with earlier tests

The timing of repeat testing depends on the situation. Do not delay follow-up when free T4 is abnormal, symptoms are significant, pregnancy is involved, or the result is markedly different from previous tests.

When to Contact a Healthcare Professional

Arrange medical follow-up if:

Your TSH is outside your laboratory’s reference interval
An abnormal result persists on repeat testing
You have symptoms of hypothyroidism or hyperthyroidism
You notice swelling in the front of your neck
You are pregnant or planning pregnancy
Your child has an abnormal thyroid result
You take thyroid medicine and your TSH has changed
You develop a rapid or irregular heartbeat
Your symptoms are getting worse

Seek urgent medical care for severe symptoms such as chest pain, fainting, severe breathing difficulty, extreme confusion, or a dangerously rapid heartbeat.

Frequently Asked Questions

What is a normal TSH level for my age?

The normal range depends on the laboratory and testing method. Mayo Clinic Laboratories currently uses 0.3 to 4.2 mIU/L for adults age 20 and older, while infants and children have age-specific ranges with higher upper limits.

Older adults may naturally have somewhat higher TSH levels. Your personal laboratory range and free T4 result are more important than a general online chart.

Is a TSH of 4.5 high?

A TSH of 4.5 mIU/L may be slightly above the range used by some laboratories but within or close to the upper limit used by others.

Its meaning depends on your age, free T4, symptoms, thyroid antibodies, pregnancy status, medication use, and previous results. A clinician may recommend repeat testing rather than making a diagnosis from one result.

Is a TSH of 5 normal for an older adult?

A TSH of 5 mIU/L may fall above a standard adult laboratory range, but mild elevations are more common in older adults. It should not automatically be assumed to represent hypothyroidism.

Free T4, symptoms, medications, thyroid antibodies, heart health, and whether the level is stable or rising should all be considered.

What TSH level means hypothyroidism?

No single TSH number confirms hypothyroidism in every person. Primary hypothyroidism is generally supported by a high TSH combined with a low free T4.

A high TSH with a normal free T4 may indicate subclinical hypothyroidism, temporary variation, medication effects, or an age-related change.

Can stress affect TSH levels?

Ordinary emotional stress does not always cause a meaningful TSH change. However, severe physical stress, hospitalization, acute illness, disrupted sleep, and certain medications may temporarily affect thyroid test results.

Why is my TSH high but free T4 normal?

This pattern may indicate subclinical hypothyroidism. It can also occur temporarily after illness, with certain medications, during inconsistent thyroid medication use, or because the laboratory range does not fully account for age.

Doctors may repeat the tests and check thyroid peroxidase antibodies before deciding whether monitoring or treatment is appropriate.

What is considered a dangerously high or low TSH?

There is no universal “dangerous” TSH number because risk depends on free T4 or T3 levels, symptoms, age, heart health, pregnancy, and the cause of the abnormality.

A very abnormal result or severe symptoms require prompt medical evaluation. Do not adjust thyroid medication based only on an online chart.

Conclusion

A TSH levels chart by age can help you understand how thyroid reference ranges change from infancy through older adulthood. Children generally have higher upper limits, most adults are evaluated using a range near 0.4 to 4.0 mIU/L, and mildly higher values may become more common with age.

The most important number is the reference interval printed on your own laboratory report. Review an abnormal result with a healthcare professional who can consider free T4, symptoms, medications, pregnancy status, previous tests, and your overall health.

This content is for informational purposes only and not medical advice.