Before undergoing testosterone replacement therapy (TRT), it's vital to obtain a number of blood tests. The main blood tests to measure are total and free testosterone, hematocrit, PSA, estradiol, HDL cholesterol and others. Pre-treatment testing provides doctors with baseline values to diagnose hypogonadism (low testosterone) and asses overall health. Baseline tests are also conducted during TRT as well, ensuring that doctors can adjust TRT dose and catch side effects before they become an issue.

Click here for the Pre- TRT panel and the TRT panel (after 6-8 weeks on TRT)

But do you know why these tests are needed or what they mean? Below, you'll find some of the main blood tests that have been shown to be affected by TRT, so doctors measure them before and during therapy to prevent or manage side effects:

Hematocrit

Hematocrit refers to the proportion or percentage of red blood cells present in your total blood volume. Your red blood cells are responsible for transporting oxygen and nutrients throughout your body. Without enough red blood cells (a condition known as anemia), your body suffers from oxygen and nutrient deprivation. On the flip side, too many red blood cells can turn your blood into a thick slurry that can seriously affect your circulation.

A normal hematocrit for an adult male is anywhere from 42 to 54%. If your hematocrit results are lower than 41%, it means you have low proportion of red blood cells. Over 55%, and you have too many.

One of the primary side effects of TRT is the production of too many red blood cells, leading to high hematocrit. High hematocrit can be lowered by blood donation or therapeutic phlebotomies (ordered by your doctor if you are not allowed to donate blood at a blood bank due to exclusion criteria). Just be careful: Do not donate blood more frequently than every 2 months since this can deplete your iron stores and make you tired.

This test is included in CBC (chemistries and blood count) panel.

PSA

Prostate-specific antigen, or PSA, is a protein that is produced in your prostate gland. It's designed to liquefy semen, which is necessary for the free swimming of sperm in ejaculate. It may also help to dissolve the cervical mucus to allow the sperm to enter the uterus for the purposes of impregnation.

Normal PSA levels for men under 40 range between 0 and 2 ng/mL, while PSA levels for men older may raise slowly.

A PSA test helps to detect extra-high levels of this protein. High PSA levels are the result of disruptions of the cellular structure of the prostate gland, which can be caused by a number of diseases--including cancer or an infection. Benign prostate hyperplasia, urinary retention, and prostatitis can be the cause of high PSA, but your doctor will want to monitor your PSA levels just to be sure the problem isn't a serious one. If PSA levels are high, your doctor may recommend a prostate exam or even a biopsy to determine the cause of your elevated PSA levels. TRT is contraindicated for men with PSA greater or equal than 4.

Estradiol

Estradiol is the primary female sex hormone, but did you know that the male body produces it from testosterone? It is produced in fat and liver cells from testosterone via the aromatase enzyme. Due to several factors like fat content, liver disease, medication effects and genetics, some men may produce more estradiol from testosterone than other men.

New information has shown that men require a special estradiol test called sensitive estradiol test. The regular test used for women may overestimate estradiol in men due to interference of inflammatory markers like C-Reactive Protein (CRP).

For the average man, estradiol levels should remain lower than 50 pg/mL, although there is little evidence of what the top of the estradiol test is in men who do not have low testosterone. If estradiol levels are higher than 50 and you start showing symptoms of high estradiol (gland growth under nipples, too much water retention), it may be necessary to take an estrogen blocker (aromatase inhibitor) . However, taking aromatase inhibitor like anastrozole should be done with careful monitoring of sensitive estradiol blood test since overdosing can cause health issues in men.

A few of the reported effects of low estradiol levels include: joint pain, eye fatigue, loss of erections, limited sensitivity in the penis, sleepiness, and excessive urination. Long term low estradiol can decrease bone density.

A few of the reported effects of high estradiol levels include: soft erections, water retention, excessive sweating, insomnia, bloating, hot flushing, brain fog, and high blood pressure.

Blood Pressure

The term "blood pressure" refers to the pressure in your arteries during the beating of your heart. There are two numbers: 1) The top number, or systolic, tells you the pressure in your arteries when the muscles of your heart contract. 2) The bottom number, or diastolic, tells you the pressure in your arteries when your heart relaxes and refills with blood in the pause between heartbeats.

Healthy blood pressure is lower than 120/80. If your blood pressure rises anywhere from 121/81 to 139/89, you are pre-hypertensive. Crack 140/90, and you suffer from hypertension. Anyone over 180/100 is in serious hypertensive crisis.

TRT can increase water retention, sodium uptake and hematocrit is some men, factors that can increase blood pressure. If your blood pressure rises too much, it can place excess strain on your blood vessels and potentially cause a crack. Should the blood vessels crack, the resulting clotting (your body's attempt to stop internal bleeding) can interfere with healthy blood flow--potentially leading to heart attacks, strokes, peripheral arterial disease, and other cardiovascular problems.

Estimated Glomerular Filtration Rate

Your glomerular filtration rate (GFR) is an indication of your kidney function. The higher your GFR, the more blood passes through the glomeruli (the filters in your kidneys that remove waste from your blood) every minute.

A healthy GFR is anywhere from 90 to 120 mL/min/1.73 m2. Senior citizens will often have lower GFR levels, due to the fact that kidney function decreases with age.

Note: It's important to understand that each lab has its own measurements, so what is "healthy" to some may be low with others.

If your GFR drops below 60 and remains at that low level for more than 3 months, it's an indication of chronic kidney disease.

Liver Enzymes

Your liver is responsible for a number of important functions, such as breaking down nutrients, producing the proteins that clot your blood, and eliminating toxins. The enzymes produced by your liver are responsible for carrying out these functions.

However, if the liver suffers damage, those enzymes tend to leak into your bloodstream. High levels of liver enzymes are a good indicator that your liver has been damaged

ALT and AST are the two most common liver enzymes. AST should be anywhere from 10 to 40 units per liter of blood, and ALT should be from 7 to 56 units in every liter of blood. Be aware that exercise may increase these two enzymes in a non-clinically significant way. Only oral testosterone replacement has been shown to increase liver enzymes.

TSH

Thyroid-stimulating hormone, or TSH, is a hormone produced by your pituitary glands in order to stimulate your thyroid gland to produce T3 and T4 hormones. These thyroid hormones play a role in your body's metabolic function.

Normal TSH levels should be between 0.5 and 3.5 U/ml (different guidelines show different upper TSH levels). Many educated doctors test for free T3 and free T4 (the unbound thyroid hormones) when TSH is over 3 since they believe this will provide a better picture of thyroid health.

If TSH levels are low, it's an indication of hyperthyroidism. If TSH levels are very high, it's an indication of hypothyroidism.

Free T3

Free T3 refers to unbound T3 (thyroid) hormone in your bloodstream. T3 is the more important of the thyroid hormones, but it can only be produced from T4. This means your body needs to produce T4 then turn it into T3. Once the T3 is unbound from the protein molecules, it can then be used by your body to stimulate metabolic function in all your cells.

Normal Free T3 levels are anywhere from 230 to 620 pg/d.

If free T3 is low, your doctor may test for thyroid antibodies to ensure that you do not have an autoimmune disease called Hashimoto’s.

Total Testosterone

Total testosterone refers to all of the testosterone circulating in your body. Some testosterone circulates freely, while some is bound to protein molecules.

The whole point of TRT is to increase your testosterone levels. A normal testosterone range is anywhere from 350 to 1070 ng/dL.

Low testosterone can cause low mood, sex drive, fatigue and other symptoms. In some men, too much testosterone in the body can lead to excessive estradiol , acne, oily skin, hair loss, testicular shrinking, and increased blood viscosity due to high red blood cells .

Free Testosterone

Free testosterone refers to the testosterone circulating in your body that is NOT bound to protein molecules like albumin and sex hormone binding globulin. It is believed that your body is more easily able to use free testosterone. It usually runs at about 2 percent or higher of total testosterone.

Ferritin

Ferritin is a protein that is responsible for storing iron and releasing it when your body needs to produce red blood cells. If you suffer from an iron deficiency, ferritin levels are likely to be low. Ferritin levels also fall when you give blood (a common method of lowering hematocrit).

Normal ferritin levels for men is anywhere from 30 to 300 ng/mL. However, if ferritin levels are too low (after a blood donation), your body is unable to store iron, meaning it will not be able to produce new red blood cells.

If you are considering donating blood to lower your hematocrit, it's a good idea to check your ferritin levels first. Your body needs enough of this protein to reproduce the red blood cells you are donating

HDL Cholesterol

High density lipoprotein, also known as HDL cholesterol, is the "good" type of cholesterol. It's responsible for counteracting the effects of low-density lipoprotein, or LDL cholesterol. Low HDL and high LDL may lead to a wide range of cardiovascular problems, including blocked arteries, stroke, heart attack, and peripheral arterial disease. According to experts, even a 5 mg/dL decrease in HDL cholesterol can increase your risk of coronary heart disease by as much as 25%

Normal HDL cholesterol levels are anything above 40 mg/dL. Unfortunately, decreased HDL is a known side effect of TRT in some men using higher testosterone doses. Your doctor will monitor HDL cholesterol via a lipid panel in order to ensure that you are not at risk for heart disease.

Click here to educate yourself about testosterone replacement's potential side effects and how to prevent / manage them.