Is fasting required for testosterone blood test?

Fasting is not required for a routine testosterone blood test. However, there are some factors related to fasting that can impact testosterone levels in the blood and therefore the test results. When getting tested for testosterone, it is best to be consistent from one test to the next in terms of fasting or non-fasting. Comparing results from a fasting vs non-fasting state can make interpretation complex. What impacts testosterone levels? Testosterone production follows a daily circadian rhythm with levels highest in the morning. Levels then fall throughout the day. Factors that can impact testosterone measurements include:

Time of day - Levels peak in the early morning so testing is often recommended shortly after waking
Age - Testosterone declines naturally as men age
Sleep - Poor sleep can lower testosterone
Stress - Both physical and emotional stress can reduce testosterone
Medications - Several prescription medications impact testosterone

Should I fast for the test?

Fasting is not required for routine testosterone testing
If comparing levels to a previous test, consistency is ideal in terms of fasting state
Eating food does not significantly impact testosterone measurements
Do not make major diet changes prior to the test

The impacts of fasting include:

Fasting can slightly increase testosterone levels
Fasting can alter levels of SHBG - a protein that binds testosterone
Refeeding after fasting can temporarily lower testosterone

Overall, non-fasting is fine for most routine testing circumstances. Ask your doctor if fasting is recommended for your specific situation.

When are testosterone levels checked?

Common reasons testosterone is measured include:

Suspected hypogonadism - testosterone deficiency
Monitoring testosterone therapy
Infertility evaluations
Issues with sexual function
In adolescent boys - delayed puberty

Diagnosing low testosterone requires:

A thorough medical history
Physical exam
Blood test - often done in the morning
Potentially repeat testing

Symptoms that prompt testing may include:

Low energy and fatigue
Difficulties with erections
Reduced muscle mass
Mood disturbances - depression

Treating hypogonadism:

If low testosterone is detected, treatment may help alleviate symptoms.
Treatment options include medication, lifestyle changes, and monitoring.
Work closely with your endocrinologist to develop the most appropriate treatment plan for your needs.