As this process is very simple there is an important fact to be aware of; there is no cure for low testosterone levels, we can only treat the symptoms, we cannot reverse it permanently. Once your levels become naturally low they will remain that way for the rest of your life unless you undergo therapy and in most cases without therapy they will only continue to decline, increasing the symptoms overall effects. However, therapy is so simple and pain free that although it must be continuous you will find it no more bothersome than pouring yourself a bowl of cereal. If you do begin therapy and abruptly stop you should be aware, your levels will fall fast and dramatically.
In a 2011 randomized controlled study, researchers recruited 54 healthy men whose mean 25(OH)D levels were in the deficiency range for a year-long intervention. They divided the subjects into two groups. The first group of 23 men had an average serum 25(OH)D of nmol/L and took a daily placebo. The second group of 31 men had an average serum 25(OH)D of nmol/L and took a daily 3332-IU vitamin D supplement. After the trial was finished, the researchers observed a significant increase in total testosterone from nmol/L to nmol/L in the supplement group. 19 In contrast, there were hardly any changes in testosterone concentrations in the placebo group. 19 These findings suggest that men deficient in vitamin D who take a proper vitamin D supplement may fix low levels of low testosterone.
But I'm not more aggressive—a behavior change often tied to testosterone. That's not surprising to Robert Sapolsky, ., a neuroendocrinologist at Stanford University and a leading researcher on stress and behavior. "It's really not the case that testosterone 'causes' aggressive behavior," he says. "Instead, it makes the brain more sensitive to social cues that trigger aggression. And in support of that, a guy's testosterone level isn't a very good predictor of how likely he is to be aggressive."