Testosterone bloodwork TikTok: what those results actually mean

What did @louisphillips12 actually say?

The claim is simple: "excessive training is negative towards your testosterone production." Louis, a self-described natural athlete training for a marathon, got blood work done because he was worried about his hormone levels. The results came back fine. His testosterone was "sitting in a great spot" and his hemoglobin was "fantastic." He ends with a nudge to get blood checked if you train hard.

This is a pretty responsible video, honestly. He's not selling anything obvious, he's sharing a genuine health concern, and he actually followed through on getting tested. The core message, that heavy endurance training can affect hormones and you should check, is not wrong. But the framing leaves out a lot of important detail that changes how worried any individual runner should actually be.

Does the science back this up?

Yes, partially, but it's more complicated than "excessive training lowers testosterone." The relationship between endurance training volume and testosterone is real but context-dependent, and the evidence does not support blanket alarm for every runner.

Research does show that high-volume endurance training can suppress the hypothalamic-pituitary-gonadal (HPG) axis. A study by Hackney et al. (2020, Current Sports Medicine Reports) confirmed that male endurance athletes can show chronically lower resting testosterone compared to sedentary men, particularly when training loads are high and caloric intake is insufficient. The key modifier there is energy availability. Relative Energy Deficiency in Sport (RED-S), formerly called the female athlete triad, affects male athletes too, and low energy availability is often the actual driver of suppressed testosterone, not training volume alone.

A 2021 review by Elliott-Sale et al. in Sports Medicine found that when male athletes maintain adequate caloric intake, testosterone suppression from training alone is modest and often transient. So the claim that training is inherently "negative" toward testosterone oversimplifies the mechanism significantly.

What did they get wrong (or right)?

He got the instinct right and the mechanism partially wrong. Getting blood work done proactively as a heavy trainer is genuinely good practice. Hemoglobin is a smart marker to check for endurance athletes, since iron-deficiency anemia is common in runners and directly affects performance and recovery. Credit where it is due.

Where the video falls short is in treating "excessive training" as a standalone cause of testosterone suppression without mentioning the variables that actually matter: caloric deficit, sleep quality, cortisol load, and training periodization. Lore et al. (2021, Journal of Clinical Endocrinology and Metabolism) found that short-term intense training caused transient testosterone drops that normalized within days of recovery. A single snapshot blood test, which is what Louis got, may not tell you much about chronic suppression either. Testosterone levels fluctuate throughout the day, with peak levels typically in the morning. One test is a data point, not a diagnosis.

His hemoglobin result being "fantastic" is good news, but he does not mention whether he tested ferritin, which is often a better early indicator of iron status in runners before hemoglobin drops.

What should you actually know?

If you are a male endurance athlete, your testosterone is more likely to be suppressed by undereating than by training itself. Marathon prep often coincides with high mileage and caloric restriction, which is the actual risk combination. Louis does not mention his diet or energy intake at all, which is the missing variable in his own story.

If you want useful blood work as a runner, testosterone total and free is a good start, but add ferritin, vitamin D, a full blood count, and cortisol if your clinician agrees. A single testosterone reading without a morning collection protocol and a follow-up test is limited in clinical value.

The recommendation to get blood work checked if you train hard is solid advice. Just know that "my results came back fine" does not mean the panel was comprehensive, and one good result during a specific training block does not guarantee hormonal stability across a full season.