Do You Need to Fast for a Testosterone Test?

Author: Nelson Vergel

How Long to Fast Before a Testosterone Blood Test: Do You Need To?

About 5 million American men suffer from low testosterone levels. This is also known as hypogonadism and can have significant effects on your life. Hypogonadism (testosterone deficiency) is diagnosed by running multiple tests.

Patients get one or more testosterone tests to measure their levels. But recent studies found out that your testosterone levels can be affected if the tests were done while fasting. In other words, having a meal before a testosterone test can change the results. Read on to find out more about the correlation between testosterone levels and fasting.

How to Test for Low Testosterone?
What is the correlation between fasting and testosterone?
Study 1 - Testosterone went down significantly after an oral glucose load
Study 2 - Eating a meal can lower testosterone levels by a lot
Key Takeaway for Future Testosterone Testing Protocols

About 5 million American men suffer from low testosterone levels. This is also known as hypogonadism and can have significant effects on your life.

Hypogonadism (testosterone deficiency) is diagnosed by running multiple tests. Patients get one or more testosterone tests to measure their levels. But recent studies found out that your testosterone levels can be affected if the tests were done while fasting.

In other words, having a meal before a testosterone test can change the results. Read on to find out more.

What is a Testosterone Test?

A testosterone test is a medical test to measure the level of testosterone in your blood. Testosterone is a hormone produced by the adrenal glands and gonads (ovaries in females and testes in males) that is important for the development and maintenance of male reproductive tissues, bone density and muscle mass. In females, testosterone is present in smaller amounts and helps in the growth and development of bones and muscles.

Why is a Testosterone Test Performed?

A testosterone test is performed to diagnose and monitor various medical conditions related to abnormal testosterone levels. The test can help identify:

Testosterone Deficiency (Hypogonadism): In males, low testosterone levels can cause low sex drive, fatigue, and decreased muscle mass.
Testosterone Excess (Hyperandrogenism): In females, high testosterone levels can cause excessive hair growth, acne, and irregular menstrual cycles.
Polycystic Ovary Syndrome (PCOS): This common endocrine disorder in females is characterized by high testosterone and androgen excess.
Adrenal Gland Disorders: Conditions like Cushing’s syndrome can cause abnormal testosterone production.
Monitoring Therapy: It’s also used to monitor testosterone levels in individuals undergoing testosterone replacement therapy or androgen deprivation therapy.

Preparing for a Testosterone Test

To prepare for a testosterone test:

Schedule the Test in the Morning: Testosterone levels are highest in the morning, so schedule your test early in the day.
Fasting: Don’t eat or drink anything but water for at least 8 hours before the test. Fasting will give you accurate results.
Inform Your Doctor: Tell your doctor about any medications or supplements you are taking, as they may affect testosterone levels.
Wear Comfortable Clothes: Wear loose and comfortable clothes and avoid tight sleeves that may make it hard to draw blood.
Plan Your Visit: You will be at the testing facility for about 30 minutes, but the blood draw will only take a few minutes.

By doing these you can get the most accurate testosterone test results.

How to Diagnose Low Testosterone?

Testosterone levels are highest in the morning for all healthy males. They start to drop after 11 am and continue to drop towards the end of the day. Testosterone tests are done in the morning because that’s when the levels are highest.

If a person sees the classic signs of low testosterone, a test might be required to check this out. These signs are low sex drive, poor concentration, fatigue and even depressive symptoms. But multiple tests are needed to confirm if the person is hypogonadal or not. A testosterone levels test measures the amount of testosterone in a blood sample.

For example, your doctor might check your FSH and LH levels. These hormones are produced by the pituitary gland and trigger the testosterone and sperm production in the testicles.

Depending on the lab, a healthy male should have a testosterone measurement between 350 ng/dl and 1,250 ng/dL. If below 350 ng/dl and you have low testosterone symptoms, you might be considered hypogonadal. Testosterone levels vary depending on the time of day, diet, age, fitness level and other factors.

As mentioned earlier, testosterone tests are done in the morning when testosterone is at its peak. Labs and doctors don’t require patients to fast before a testosterone test. But some studies suggest that fasting before a testosterone test can affect the results.

What’s the connection between Fasting and Testosterone Levels?

In simple terms, fasting means not eating for a certain period of time, usually 8 to 12 hours. This also includes not drinking anything that makes your organs work to process them, like drinks, milk, etc.

Many blood tests require patients to fast before drawing a sample. A standard glucose test is a good example of this. If you eat something and then do a glucose test, you might be labeled as diabetic.

That’s because your body didn’t get a chance to process the glucose in your blood, and it will show up in the test. Scientists believe that fasting is also important when testing testosterone through blood tests.

In short, eating before your test will temporarily lower your testosterone levels. This can lead to a false diagnosis of hypogonadism if your normal T level is around 400-500 ng/dL. Such findings also mean retesting subjects who were initially diagnosed with low testosterone.

Let’s look at a few studies and see the correlation between fasting and testosterone tests in more detail. You’ll see how a glucose load or a full meal can affect the total and bioavailable testosterone levels hours after ingestion.

Study 1 - Testosterone Decreased Significantly After an Oral Glucose Load

This study was done on 74 men. The average age of the participants was around 50, give or take a few years. The study was done in 2012, and it was a standard 75-g oral glucose tolerance test.

An oral glucose tolerance test measures how well your body can process glucose in the blood after you drink a sweet drink they give you at the lab. If you process it fast, your glucose tolerance is good. If it takes too long to process, it’s usually associated with diabetes or other health problems.

Almost 60% of the men in the study had normal glucose tolerance. More than 10% were newly diagnosed with diabetes, and about 30% had impaired glucose tolerance. Blood was drawn from each participant at the start of the study and at 30, 60, 90, and 120 minutes, respectively.

Other hormones and substances were also measured, such as insulin, leptin, sex hormone-binding globulin (SHBG), and total testosterone levels. None of these individuals had low testosterone at the start of the study.

But the results were surprising. The study showed that testosterone levels decreased by 25% after glucose ingestion. That’s a big drop considering most of the participants had normal glucose tolerance.

To put it into perspective, if an individual starts with an average testosterone level of 500 ng/dl, a 25% decrease would bring him down to 375 ng/dl. That’s close to the bottom of the normal testosterone range.

Interestingly, the testosterone suppression was still present after 120 minutes when blood samples were drawn for the last time. 10 of the participants could qualify for hypogonadism at the end of the study as their testosterone levels went below the baseline.

This study shows how important it is to test for testosterone in a fasted state. A simple glucose load can lower total testosterone levels and qualify someone for hypogonadism.

Study 2 - Eating a Meal Can Decrease Testosterone Levels

Let’s look at another study that shows the correlation between testosterone levels and fed or fasting state. This study shows how a 550-calorie meal of protein, fat and carbohydrates can affect testosterone levels.

11 healthy men participated in this study. They were non-smokers, had no medical treatment, and had normal BMI. The average age was 43 years, and they had no significant medical history.

In the first part of the study, the participants were given a 550-calorie meal of buttermilk, cheese, ham, orange juice, and other foods. Blood was drawn at various intervals. The study also measured other hormones such as LH, SHBG, and glucose. Free testosterone, the unbound fraction and biologically active, was also measured.

The participants finished the meal in about 15 minutes. The foods were varied, as the study designers wanted to mimic a meal that most men would eat on a daily basis.

Before the meal, the participants were told to fast for 12 hours. They were also instructed not to have sex or do any strenuous exercise that would affect their testosterone levels.

The same procedure was repeated a few weeks later with the same participants. This time they only fasted for 12 hours and didn’t eat after. Blood was drawn in the fasting state, and all other parameters were the same.

When the two experiments were compared, the results were striking. In both groups, the initial fasting testosterone levels were the same. LH and SHBG were unchanged.

But in the fed group, testosterone levels decreased 15 minutes after meal ingestion. And 30 minutes after the meal. Other hormones and parameters were the same; just total and bioavailable testosterone levels went down.

Upon reviewing the results, the experts found out that the decrease in testosterone was 30%. This was true for all participants with no exceptions. This study shows how testing for testosterone in a fasted state is different from testing in a fed state.

Takeaway for Future Testosterone Testing Protocols

The scientific literature on sexual medicine says that food intake can affect testosterone levels. But the standard testosterone test protocol doesn’t require fasting before the test. The studies above open up a potentially big change in how testosterone tests are done.

Also, there was no significant difference in LH, SHBG, and other hormones among the participants. This means the hypothalamic-pituitary-testicular (HPT) axis was not really affected by food or glucose intake, but testosterone production was. It’s believed that insulin, a hormone produced by the pancreas when we eat to process glucose, can temporarily decrease testosterone production at the testicular level.

If you think you have low testosterone, order these testosterone tests online at an affordable price and see how your hormones are doing.