Lab Method Matters for Hormone Testing

Discover how lab methods affect hormone testing results, the importance of accurate measurements, and tips for reliable hormone assessments.

When checking estrogen or testosterone levels, the number you get depends partly on how the lab measured it. Labs use two main methods, and they don't always give the same answer.

The two methods

• Immunoassay: The most common and cheaper option. It works well when hormone levels are fairly high, like estrogen in women menstruating regularly.
• LC/MS (mass spectrometry): More precise, especially at low levels. Experts and the CDC consider it the gold standard for hormone testing, though it is more expensive.

When LC/MS is the better choice

• Men, children, and postmenopausal women, since their estrogen levels are naturally low
• People on low-dose hormone therapy or estrogen-blocking drugs
• Cases where accuracy is critical, such as checking bone fracture risk or puberty problems
• Testosterone testing in women, including after menopause

What can throw off your results

• Biotin: This vitamin (common in hair and nail supplements) can make results falsely high or low. Stop taking it at least 72 hours before your blood draw.
• Certain medications: The breast cancer drug fulvestrant (Faslodex) can skew estrogen results on immunoassay tests.
• Birth control pills: These can make testosterone look higher than it is on some tests.
• Antibodies: Rarely, antibodies in your blood can interfere with immunoassays.

What "2nd generation" testosterone means

This is an upgraded immunoassay introduced in 2007. It does a better job at low levels than older versions. But other substances in your blood, like the hormone DHEA, can still affect it, and its results don't match LC/MS.

Free vs. total testosterone

• Most testosterone in your blood is attached to a protein called SHBG. "Free" testosterone is the unattached part your body can use.
• Labs measure free testosterone in different ways, so results and normal ranges can vary a lot between labs.
• A reliable approach is to calculate free testosterone from your total testosterone, SHBG, and albumin. If you're getting testosterone checked, ask that SHBG be included.

Why testosterone matters after menopause

• SHBG drops by about 43% around menopause, which raises the share of free testosterone.
• In postmenopausal women, higher testosterone has been linked to a higher risk of heart disease and metabolic syndrome, and to more severe mood symptoms.
• Your practitioner may check testosterone along with other markers like cholesterol, blood sugar, thyroid, and vitamin D.

Tips for getting useful results

• Use the same test method each time so you can compare results over time.
• Hormones can swing a lot, especially during perimenopause, and results should be read alongside your symptoms.
• Tell your practitioner about all supplements and medications.
• Check your lab report to see which method was used.

Learn More at ODX:

What’s the difference between estradiol immunoassay and LC/MS testing, and when is each method more appropriate?

What are your thoughts on assessing testosterone in a Post menopausal patient not on Testosterone replacement, is the LS/MS methodology recommended?

Why might estradiol (ECLIA) test results sometimes come back unusually high or inconsistent? Can supplements or medications interfere with results, and when is LC/MS testing a better option?

Please explain what is meant by 2nd generation Testosterone.

Question about LabCorp's Free Testosterone: why did the result for LabCorp's Free Testosterone change from what was on the original report to a different result in the FHR from Optimal DX, and why are the ranges so different?

Optimal DX FYI: High-dose Biotin Interferes with Lab Tests