39% of men 45 years or older are estimated to suffer from hypogonadism… 
It’s important to remember the human body is a very complex organism. When it comes to some of the symptoms discussed in this article, low testosterone may be the most likely culprit, but it does not necessarily mean it always is the underlining cause. With that said, if you relate to two or more of any of the below symptoms you may want ask your doctor to have a simple blood panel run to see if your testosterone levels are in the normal range.
1- Low Sex Drive
Low sex drive may be the number one sign of low testosterone.  Fluctuations in libido are normal to an extent, but if you find yourself being sexually disinterested for any prolonged period of time, you very likely have low T. You might find yourself saying, but it’s not that I have low testosterone, I’m only disinterested because of all the stress I’m under. But what you should know is, stress actually causes low testosterone. The stress hormone cortisol can actually convert your body’s free testosterone into estrogen, leading to a number of unwanted side effects for men including diminished libido.
2- Difficulty Building Muscle
The main reason men have a distinct gender advantage when it comes to building muscle is the simple fact that men on average have 10 times the testosterone. As a man’s testosterone diminishes, so does his ability to build muscle.  If your goal is to build muscle or simply maximize your athletic performance one of the most important things for you to do is make sure your testosterone is as high as you can naturally get it.
3- Erectile Dysfunction
There are a number of biological issues beyond low T that can cause ED. If you find your sex drive is very high but you still can’t achieve adequate erections than low testosterone may not be the culprit. But if you suffer from ED and have a relatively low sex drive, then your testosterone levels are likely the cause of your ED. 
4- Orgasm Trouble
Men with low testosterone, especially low free testosterone, often report having a lack of sexual sensation that typically leads to difficulty attaining orgasms. This is a good indication of low testosterone, but if no other symptoms are present, low T likely isn't the cause. 
5- Belly Fat
Of course, testosterone is not the main cause of unwanted weight gain, but there is a connection. There have been a number of observational research studies that have shown increased androgenicity (production of testosterone) has a positive relation to favorable body fat distribution. In other words, men with low T levels tend to gain belly fat. 
Depression is a very serious subject, and I’d like to point out the connection between hypogonadism and depression. But let’s be very clear, the research I am referring to was done on a relatively small sample size (157 men) and it showed a strong correlation but not necessarily causation. With all that said, the study mentioned showed 1.94 times higher relative risk of having overt depression in men with hypogonadism. 
Hormonal imbalances, especially with regards to low testosterone in men, can cause chronic fatigue. Periodic fatigue is relatively normal, but if you frequently feel overwhelmed with exhaustion and a lack of motivation that is a major health concern and may be indicative of hypogonadism. 
8- Slow Recovery
The higher your testosterone is the faster your body will bounce back from workouts. If you find that you become sore from workouts for an abnormally long period of time you likely have low testosterone or a poor diet.
Mood changes can come on slow and often times go unnoticed by the individuals experiencing them. Nevertheless, the changes can have very negative effects and aren’t overlooked by friends and family. If you suspect that you are more irritable than normal it’s a good idea to ask those that are closest to you. This is another strong sign that your testosterone is not what it should be. 
This is likely the surest sign there is that you have very low levels of testosterone and higher than normal estrogen. If you haven’t heard of gynecomastia, it is essentially the swelling of the breast tissue in men, and it’s more common than you might think. There are approximately 200,000 cases of gynecomastia in the U.S. alone every year. 
What are your options?
Testosterone Replacement Therapy
Under certain circumstances, TRT can be great, but devastating in other. It is crucial that you understand the risks of TRT before making the decision to do it. First, let’s talk about why it can be dangerous. When you take exogenous testosterone your body tends to stop naturally producing testosterone on its own. And because testosterone production is a critical component of spermatogenesis this can lead to infertility, although most men are able to regain fertility within 1 year of quitting TRT. Additionally, your body can become depended on exogenous testosterone causing your testicles to atrophy and even lose the ability to produce testosterone on their own. If you cannot get your testosterone to a healthy level naturally, then you may want to consider asking your doctor if TRT is right for you.
Your body produces testosterone while you’re sleeping, so in order to maximize testosterone production, you will need to ensure you’re getting enough quality sleep. Take for example, this observational study done by the University of Chicago Department of Medicine. Subjects were split into two groups, group one slept for 4-hours per night and group two slept for 8-hours per night, and both groups had their testosterone tested upon waking in the morning. Group one (4-hours sleep) had an average testosterone of right around 315 ng/dL, whereas, group two (8-hours sleep) had average testosterone levels of 675 ng/dL. This study very clearly highlights the importance of sleep when maximizing testosterone production. 
While staying on the subject of sleep, let’s talk about the difference between red and blue light. You see, your circadian rhythm is based on light. When you see a bright blue light that is an indication that is daytime and your body should be awake, but unfortunately many electronic devices emit the same daytime blue light. But companies are realizing this mistake and are offering settings to automatically dim and change the color tone at night to avoid disturbing circadian rhythm. So be proactive and make sure you enable these feature (I use F.lux on my computer) and avoid bright blue lights at night, and this will improve your sleep quality and indirectly improve many other health biomarkers including testosterone production. 
Let’s first touch on diet. There’s almost no limit to how much can be written on the effect diet has on testosterone. So I’ll just mention one study and then give a summary of what foods to avoid and which ones will optimize testosterone production. There was a very interesting study done with twenty-six college-aged resistance trained men that were split into two groups and given very different diets.  One group was given a very tradition western diet comprised of 50% carbohydrate, 25% fat, and 20% protein. And the second group was given a high-fat low-carb diet. The purpose of the study was to determine the safety and effect on testosterone of a high-fat low-carb diet. For those that view dietary fat as a negative thing, the results might surprise you. There were no differences in any of the safety parameters measured, and while the high-fat group did see an increase in cholesterol, it was HDL, the good stuff. But here’s where it gets really good. Total testosterone increased significantly in the low-carb high-fat group (118 ng/dl) as compared to the western diet group (-36 ng/dl) while insulin sensitivity decreased in the western group (not something you want).
In summary, a low carb diet high in saturated fats and protein will not only significantly increase your testosterone, it will improve many other health parameters.
A good testosterone booster is certainly the easiest solution to dramatically increasing testosterone, but if you really want the best results possible, you will need to optimize your sleep as well as diet.
While admittedly my opinion on testosterone boosters is bias, I'll give it anyway. I believe TestMax HD is the best testosterone booster on the market, and here’s why. It works by giving your body the micronutrients it needs to maximize testosterone production while also reducing cortisol by an average of 30%. And you may only associate cortisol with stress, anxiety, and fatigue but cortisol also converts your body’s free testosterone into estrogen, via aromatase enzymes. And the last thing I’ll mention about TestMax HD is that it has a 200% money back guarantee if it doesn’t raise your testosterone 25% or more within 30-days.