From the Guidelines
Testosterone testing does not require fasting, but for the most accurate results, it is recommended to have the test done in the morning, ideally between 7 and 10 AM, when testosterone levels are naturally at their highest. This timing is particularly important for men, as testosterone levels fluctuate throughout the day 1. Some healthcare providers might recommend repeat testing on different days to account for natural variations. While fasting isn't necessary, certain factors can affect testosterone levels, including some medications, alcohol consumption, and recent intense exercise. If you're taking medications like corticosteroids, opioids, or certain anticonvulsants, inform your healthcare provider as these can influence test results 1. The test itself is a simple blood draw that measures both total testosterone (bound and unbound) and sometimes free testosterone (the unbound, active form) to provide a comprehensive picture of your hormone status.
Key points to consider:
- Testosterone levels naturally fluctuate throughout the day, with the highest levels typically in the morning 1
- Certain medications, such as corticosteroids, opioids, or certain anticonvulsants, can affect testosterone levels 1
- Repeat testing on different days may be recommended to account for natural variations in testosterone levels 1
- A morning total testosterone level should be measured using an accurate and reliable assay, and in men who have total testosterone levels close to the lower limit, it is reasonable to determine free testosterone concentrations 1
It's essential to follow the healthcare provider's recommendations for testosterone testing, as they will consider individual factors and medical history to ensure accurate results and appropriate treatment.
From the Research
Testosterone Testing Requirements
- Testosterone testing may require fasting, as some studies suggest that glucose load or meals can lower testosterone levels in healthy men 2, 3, 4.
- A study published in 2019 found that oral glucose load and mixed meal feeding lowered testosterone levels in healthy eugonadal men, with a mean drop of 100 ng/dL and 123 ng/dL, respectively 2.
- Another study published in 2022 recommended that testosterone levels should be measured in 2 or more fasting samples obtained in the morning 3.
- However, a study published in 2021 found no significant difference between fasting and non-fasting testosterone levels in men, suggesting that fasting may not be necessary for diagnosis 5.
- It's also worth noting that the effect of fasting on testosterone levels may vary between individuals and populations, such as women during the childbearing period, where fasting testosterone levels were found to be significantly higher than non-fasting levels in apparently healthy women 6.
Key Findings
- Testosterone levels can be affected by glucose load or meals 2, 4.
- Fasting may be recommended for accurate measurement of testosterone levels 2, 3, 4.
- However, some studies suggest that fasting may not be necessary for diagnosis 5.
- The effect of fasting on testosterone levels may vary between individuals and populations 6.