From the Guidelines
Fasting is not required before checking testosterone levels, but it is recommended to have the blood test done in the morning, typically between 7 and 10 AM, when testosterone levels are naturally at their highest. This timing provides the most accurate baseline measurement, as testosterone follows a circadian rhythm, with levels peaking in the morning and declining throughout the day 1.
Some key points to consider:
- Testosterone levels can be measured at any time of day, but morning testing is preferred for consistency and accuracy 1.
- The Endocrine Society and other medical organizations recommend measuring morning total testosterone levels using an accurate and reliable assay 1.
- In men with diabetes, testosterone replacement may have benefits, including improved sexual function, well-being, muscle mass and strength, and bone density, but the decision to treat should be individualized and based on a thorough medical evaluation 1.
- Further testing, such as luteinizing hormone and follicle-stimulating hormone levels, may be needed to determine if a patient has hypogonadism and to guide treatment decisions 1.
It's essential to follow the specific instructions provided by the healthcare provider or laboratory, as they may have specific requirements or recommendations for testosterone testing 1.
From the FDA Drug Label
Prior to initiating testosterone enanthate injection, confirm the diagnosis of hypogonadism by ensuring that serum testosterone concentrations have been measured in the morning on at least two separate days and that these serum testosterone concentrations are below the normal range
The answer to whether checking testosterone level needs to be done in a fasting state is not directly addressed in the provided drug label. Fasting status is not mentioned as a requirement for measuring serum testosterone concentrations.
- The label only mentions that serum testosterone concentrations should be measured in the morning on at least two separate days.
- There is no information regarding the need for fasting before checking testosterone levels. 2
From the Research
Testosterone Level Checking Requirements
- The requirement for fasting before checking testosterone levels is a topic of discussion among medical professionals and researchers.
- A study published in 2021 3 found no significant difference between fasting and non-fasting testosterone levels in men, suggesting that fasting may not be necessary for diagnosing hypogonadism.
- However, another study published in 2018 4 recommends measuring fasting morning total testosterone concentrations as the initial diagnostic test for hypogonadism.
- A more recent study published in 2023 5 found that in women during the childbearing period, fasting testosterone levels were significantly higher than non-fasting levels, but this difference was not seen in women with symptoms such as hirsutism or menstrual irregularities.
Variability in Laboratory Reference Values
- Laboratory reference values for testosterone can vary widely, with different assays and reference ranges used by different laboratories 6.
- This variability can make it challenging to diagnose hypogonadism and other androgen disorders.
- Accurate measurement of total and free testosterone levels is essential for making a diagnosis, and should ideally be done using a reliable assay such as liquid chromatography tandem mass spectrometry 7.
Recommendations for Testosterone Level Measurement
- The Endocrine Society recommends measuring fasting morning total testosterone concentrations as the initial diagnostic test for hypogonadism 4.
- However, the study published in 2021 3 suggests that non-fasting testosterone levels may be sufficient for diagnosis, which could simplify the testing process and reduce the burden on patients.
- Further research is needed to determine the optimal approach for measuring testosterone levels and diagnosing hypogonadism.