Thyroid-stimulating hormone (TSH) is produced by your pituitary gland, which helps regulate hormone production and metabolism throughout your body. TSH helps your thyroid gland make other hormones essential to your metabolism, such as thyroxine. It also contributes to your overall energy levels, nerve functions, and much more.

The typical range of reference for TSH levels is anywhere between 0.4 and 4.9 milliunits per liter (mU/L). A recent study suggests that the normal range should be more like 0.45 to 4.12 mU/L.

TSH can vary wildly based on your age, sex, and stage of life. For example, a 29-year-old woman may have normal TSH around 4.2 mU/L, while an 88-year-old man may reach 8.9 mU/L at their upper limits. And stress, your diet, medications, and having your period can all make TSH fluctuate.

TSH levels change inversely with how much thyroid hormone is in your body. Think of your pituitary gland as a thyroid thermometer:

  • Abnormally high TSH levels mean that your thyroid is underperforming. Your pituitary gland reacts to a lack of thyroid hormones by producing extra TSH to make up the difference. This is called hypothyroidism.
  • Low TSH levels mean that you’re producing too much thyroid hormone. Your pituitary gland responds accordingly by decreasing TSH production to get thyroid function under control. This is called hyperthyroidism.

Let’s learn more about the range of TSH levels for different groups of people and what to do if your level is too high or too low.

Here’s a breakdown of normal, low, and high TSH levels for women based on age:

Age rangeNormalLowHigh
18 – 29 years0.4 – 2.34 mU/L< 0.4 mU/L> 4.5 mU/L
30 – 49 years0.4 – 4.0 mU/L< 0.4 mU/L> 4.1 mU/L
50 – 79 years0.46 – 4.68 mU/L< 0.46 mU/L4.7 – 7.0 mU/L

Women are at greater risk for developing abnormal TSH levels during menstruation, when giving birth, and after going through menopause. Around 5 percent of women in the United States have some kind of thyroid condition, compared with 3 percent of men.

Despite claims that high TSH increases your risk for heart disease, a 2013 study found no link between high TSH and heart conditions such as a heart attack. But a 2017 study showed that older women are especially at risk for developing thyroid cancer if they have high TSH levels along with thyroid nodules.

Here are the normal, low, and high ranges of TSH levels for men:

Age rangeNormalLowHigh
18 – 30 years0.5 – 4.15 mU/L< 0.5 mU/L> 4.5 mU/L
31 – 50 years0.5 – 4.15 mU/L< 0.5 mU/L> 4.15 mU/L
51 – 70 years0.5 – 4.59 mU/L< 0.5 mU/L> 4.6 mU/L
71 – 90 years0.4 – 5.49 mU/L< 0.4 mU/L> 5.5 mU/L

Both high and low TSH can affect fertility. Men with hypo- or hyperthyroidism both had fewer normally shaped sperm.

And men are more susceptible than women to complications like irregular development of the genitals if they have high TSH. Taking thyroid hormone replacement therapy may be necessary for men to balance TSH.

TSH levels in children can vary based on their age:

Age rangeNormalLowHigh
Premature birth0.7 – 27 mU/L< 0.7 mU/L> 28 mU/L
0 – 4 days1 – 29 mU/L< 1 mU/L> 30 mU/L
2 – 20 weeks1.7 – 9.1 mU/L< 1.7 mU/L> 9.2 mU/L
20 weeks – 18 years0.7 – 64 mU/L< 0.7 mU/L> 64 mU/L

A 2008 study that closely measured TSH levels in kids from birth to as old as 18 years found wildly different TSH levels throughout their lives.

And though TSH tends to be high for the first month after they’re born, a child’s TSH levels will gradually decrease as they get closer to adulthood before rising again as they age.

The chart below shows you how to know when your TSH levels are normal, low, and high when you’re pregnant, specifically between the ages of 18 and 45:

Stage of pregnancyNormalLowHigh
First trimester0.2 – 2.5 mU/L< 0.2 mU/L2.5 – 10 mU/L
Second trimester0.3 – 3.0 mU/L< 0.3 mU/L3.01 – 4.50 mU/L
Third trimester0.8 – 5.2 mU/L< 0.8 mU/L> 5.3 mU/L

It’s important to monitor TSH levels during pregnancy. High TSH levels and hypothyroidism can especially affect chances of a miscarriage.

As a result, about 1 to 2 percent of pregnant women may receive levothyroxine (Synthroid), methimazole (Tapazole), or propylthiouracil (PTU) to help control TSH and thyroid hormone levels, especially if they have hypo- or hyperthyroidism.

If you’re pregnant and already taking this medication for abnormal thyroid hormone levels, your doctor may recommend increasing your dose by about 30 to 50 percent.

Successful treatment of high TSH and hypothyroidism during pregnancy can lower your chances of having a miscarriage. Control of TSH levels can also help prevent other pregnancy complications, such as:

Your doctor may recommend one or more of the following treatments for abnormal levels of TSH:

Hypothyroidism (high TSH)

  • daily medications, such as levothyroxine (Synthroid)
  • natural thyroxine hormone extracts and supplements
  • eating or consuming less of substances that affect levothyroxine absorption, such as fiber, soy, iron, or calcium

Hyperthyroidism (low TSH)

  • oral radioactive iodine to shrink your thyroid gland
  • methimazole (Tapazole) or PTU to keep your thyroid from making too much thyroid hormone
  • removal of your thyroid gland if regular treatments don’t work or may be threatening to your health, such as during pregnancy

Abnormal TSH can indicate that your thyroid gland isn’t functioning properly. This can lead to long-term complications if you have an underlying condition that leads to hypo- or hyperthyroidism.

Make sure you get your TSH levels tested regularly, especially if you have a family history of thyroid disorders or have seen abnormal TSH levels on previous test results.

Follow any instructions your doctor gives you to stop taking certain medications or eating certain foods before a TSH test to make sure the results are accurate. This way, your doctor can give you a treatment plan that’s best for the cause of abnormal TSH.