If your training is consistent but your results aren't — if recovery takes longer than it should, or your motivation has dropped — the problem is rarely your programme. It's usually your biology. Blood tests tell you exactly where the gaps are.
The Performance Blood Test Panel
Total Testosterone
The primary anabolic hormone. Low testosterone limits muscle gain, recovery speed, and drive.
Free Testosterone + SHBG
High SHBG binds testosterone, reducing the active fraction even when total levels look acceptable.
Ferritin
Iron stores power oxygen delivery to working muscle. Low ferritin limits endurance and recovery.
Vitamin D
Directly linked to testosterone production, muscle protein synthesis, and injury risk.
Cortisol (morning)
Overtraining elevates cortisol chronically, breaking down muscle and suppressing recovery.
IGF-1
Reflects growth hormone activity — a key driver of muscle repair and body composition.
Thyroid (TSH + free T4)
Hypothyroidism reduces metabolic rate, training capacity, and body composition response.
LH + FSH
Pituitary signals to the testes. Helps distinguish primary from secondary hypogonadism.
Oestradiol
Too high (aromatisation) reduces testosterone effect; too low impairs recovery and bone health.
Prolactin
Elevated prolactin suppresses testosterone and libido — sometimes caused by training stress.
CRP + ESR
Chronic low-grade inflammation impairs muscle repair and blunts anabolic signalling.
Fasting glucose + insulin
Insulin resistance impairs nutrient partitioning — essential for body recomposition goals.
What "Normal" Doesn't Mean for Athletes
A testosterone of 10 nmol/L is technically "within range" — but it's in the lowest quartile for adult men and will significantly impair muscle gain and recovery. Similarly, ferritin of 20 µg/L is "not anaemic" but will limit aerobic capacity and slow repair. The question isn't whether your results are abnormal; it's whether they're optimal for your training load.
When to Test
Test fasted, in the morning (8–10am), after at least one full rest day. Testosterone and cortisol have strong circadian rhythms and will be misread at other times. Avoid testing within 48 hours of a maximal session — acute exercise transiently suppresses testosterone and elevates cortisol and CRP.
What Happens After the Test?
If results reveal a deficiency, your GP will discuss your options. Low ferritin is most efficiently corrected with an IV iron infusion. Low testosterone may warrant TRT or lifestyle interventions depending on severity. Vitamin D deficiency is straightforward to treat with supplementation. Your GP will give you a clear action plan.
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