The reliable measurement of serum free testosterone requires equilibrium dialysis. This is not appropriate for clinical use as it is very time consuming and therefore expensive. The amount of bioavailable testosterone can be measured as a percentage of the total testosterone after precipitation of the SHBG bound fraction using ammonium sulphate. The bioavailable testosterone is then calculated from the total testosterone level. This method has an excellent correlation with free testosterone (Tremblay and Dube 1974) but is not widely available for clinical use. In most clinical situations the available tests are total testosterone and SHBG which are both easily and reliably measured. Total testosterone is appropriate for the diagnosis of overt male hypogonadism where testosterone levels are very low and also in excluding hypogonadism in patients with normal/high-normal testosterone levels. With increasing age, a greater number of men have total testosterone levels just below the normal range or in the low-normal range. In these patients total testosterone can be an unreliable indicator of hypogonadal status. There are a number of formulae that calculate an estimated bioavailable or free testosterone level using the SHBG and total testosterone levels. Some of these have been shown to correlate well with laboratory measures and there is evidence that they more reliably indicate hypogonadism than total testosterone in cases of borderline biochemical hypogonadism (Vermeulen et al 1971; Morris et al 2004). It is important that such tests are validated for use in patient populations relevant to the patient under consideration.

That testosterone decreases with age has been clearly established by many studies over many years in several different populations of men (Harman et al 2001; Feldman et al 2002; Araujo et al 2004; Kaufman and Vermeulen 2005). Of even greater significance is the steeper fall of the most biologically active fraction of total testosterone, non-sex hormone binding globulin (SHBG)- bound testosterone, or bioavailable testosterone (bio-T). The classical, but not the only approach to measuring bio-T, is to precipitate out SHBG (and hence the testosterone which is strongly bound to it as well) and measure the remainder as total testosterone (Tremblay 2003). Vermeulen et al (1999) have devised a less tedious and less expensive method of measuring a surrogate for bio-T, namely calculated bio-T, inserting total T, albumin, SHBG and a constant into a mathematical formulation. There is a strong correlation between actual bio-T and calculated bio-T (Emadi-Konjin et al 2003).

Epidemiological data has associated low testosterone levels with atherogenic lipid parameters, including lower HDL cholesterol (Lichtenstein et al 1987; Haffner et al 1993; Van Pottelbergh et al 2003) and higher total cholesterol (Haffner et al 1993; Van Pottelbergh et al 2003), LDL cholesterol (Haffner et al 1993) and triglyceride levels (Lichtenstein et al 1987; Haffner et al 1993). Furthermore, these relationships are independent of other factors such as age, obesity and glucose levels (Haffner et al 1993; Van Pottelbergh et al 2003). Interventional trails of testosterone replacement have shown that treatment causes a decrease in total cholesterol. A recent meta-analysis of 17 randomized controlled trials confirmed this and found that the magnitude of changes was larger in trials of patients with lower baseline testosterone levels (Isidori et al 2005). The same meta-analysis found no significant overall change in LDL or HDL cholesterol levels but in trials with baseline testosterone levels greater than 10 nmol/l, there was a small reduction in HDL cholesterol with testosterone treatment.
At the present time, it is suggested that androgen replacement should take the form of natural testosterone. Some of the effects of testosterone are mediated after conversion to estrogen or dihydrotestosterone by the enzymes aromatase and 5a-reductase enzymes respectively. Other effects occur independently of the traditional action of testosterone via the classical androgen receptor- for example, its action as a vasodilator via a cell membrane action as described previously. It is therefore important that the androgen used to treat hypogonadism is amenable to the action of these metabolizing enzymes and can also mediate the non-androgen receptor actions of testosterone. Use of natural testosterone ensures this and reduces the chance of non-testosterone mediated adverse effects. There are now a number of testosterone preparations which can meet these recommendations and the main factor in deciding between them is patient choice.
As “the ultimate guide” I want this article to be the last resource you need when it comes to boosting your testosterone. I have spent years researching this stuff, and experimenting on myself. And in case I am incomplete, I have linked out at the bottom of this page to all the best resources for increasing testosterone around the web. I truly believe there is no better resource out there than what you’re reading right now.
Yeah, you could do expensive hormone replacement. Or you could take a synthetic test booster. But at the end of the day, neither of these compare to being able to boost testosterone naturally. Nature didn’t intend for you to inject yourself with hormones. Somewhere along the line something went wrong. At your natural level, you are designed to flourish. And the world has everything available for you and your testosterone levels to do so.
Your diet is the best source of zinc; along with protein-rich foods like meats and fish, other good dietary sources of zinc include raw milk, raw cheese, beans, and yogurt or kefir made from raw milk. It can be difficult to obtain enough dietary zinc if you're a vegetarian, and also for meat-eaters as well, largely because of conventional farming methods that rely heavily on chemical fertilizers and pesticides. These chemicals deplete the soil of nutrients ... nutrients like zinc that must be absorbed by plants in order to be passed on to you.
5. Beef.  Is there a manlier food than steak? Release your inner carnivore if you want to boost your testosterone level. Lean beef is rich with zinc, saturated fat, iron, protein and magnesium. We’ve already mentioned earlier on how zinc can enhance the production of testosterone. Lean beef can be an excellent food choice, since you can increase your testosterone level and muscle mass at the same.

Withania Somnifera is another name for Ashwagandha which is an ancient herb used as a medicine. It is an adaptogen because it helps the body to handle anxiety and stress. It improves T levels along with increasing sperm production. Other than improvement in sexual performance it also helps in fat loss, strength, and stamina. It reduces the stress by reducing the output of the cortisol hormone, which acts antagonist to testosterone. This reduction helps to body to trigger the testosterone production.

For this reason I recommend doing your own research on this supplement before taking it. 5g of ground up dried powder is what was used in the studies. I recommend taking 1-2 capsules of the concentrated form from Paradise Herbs. Alternatively, the Aggressive Strength Test Booster also has MP in its formula so you may prefer to use that blend instead. 
This supplement is not only marketed to increase sexual desire, but the manufacturer also claims this testosterone booster can accelerate muscle growth, build endurance and decrease muscle pain after workouts. The main ingredient in the product is 25 mg of zinc. Additional ingredients include a proprietary blend of ginkgo biloba, cayenne pepper, tribulis terristris and maca. Recommended dosage is three capsules taken on a daily basis as a dietary supplement.
Levels of testosterone naturally decrease with age, but exactly what level constitutes "low T," or hypogonadism, is controversial, Harvard Medical School said. Testosterone levels vary wildly, and can even differ depending on the time of day they're measured (levels tend to be lower in the evenings). The National Institutes of Health includes the following as possible symptoms of low testosterone:

All the active substances available in TestoGen are fully natural. And their efficacy and safety is science-backed. So, if you don’t have individual sensitivity to the supplement ingredients and purchase the product directly from the manufacturer instead of purchasing from unknown suppliers, the likelihood of side effects during the supplementation is minimal. And the customer feedback proves this.
“Before taking Andro400, my husband weighed 290 lbs. He's a diabetic and his blood pressure was through the roof. I purchased Andro based on the reviews, and he's lost 60 - 70 lbs! ​It's enhanced him health-wise in a lot of aspects too. He used to be depressed because of his weight. The fact that he was losing weight like crazy gave him a lot of relief. He's not depressed now, he's really happy. He's more loving. And it's so exciting for me as a wife to see him happier -- it made me happier​! ​ So I'm really grateful. Andro400 gave him a lot of ​energy ​ too because of the testosterone boost.​ The 3 main things everybody's noticing are: no more​ depression, a lot more energy and ​the huge weight loss. He went from size 42 to 38, so it's like, oh my God it's WORKING!! Trust me, we've tried a lot of other things that didn't work. And that's why I'm so excited because it's actually, literally changing our lives!”
Although some men believe that taking testosterone medications may help them feel younger and more vigorous as they age, few rigorous studies have examined testosterone therapy in men who have healthy testosterone levels. And some small studies have revealed mixed results. For example, in one study healthy men who took testosterone medications increased muscle mass but didn't gain strength.