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Can a Blood Test Tell You How Athletic You Are?

Athleticism is hard to define - the athleticism of a marathon runner is clearly different from that of a powerlifter, and the fitness requirements of a gymnast are different to those of a football player. And yet, all would be considered athletic.


As you might expect given this variety in athleticism, there is no single blood test that can tell you how athletic you are. There are, however, blood tests that are useful to help you assess your general state of health and fitness and others that enable you to monitor for issues such as overtraining and to check your nutritional status to help you optimise performance.

Athletes running

Basic Markers of Health

Athletes should be fit, with high exercise levels and a healthy diet leading to lean muscle mass and optimal body function. To confirm the effectiveness of their training regime, athletes may consider several basic blood tests:

  • Blood Sugar Levels and HbA1C: A blood sugar level and an HbA1C (a longer-term measure of blood sugar levels) are useful to show that blood sugar levels are as you would expect them to be for an athlete. Regular exercise reduces blood sugar levels and high levels suggestive of pre-diabetes or diabetes should prompt an immediate reassessment of diet and exercise choices.

  • Cholesterol and Triglycerides: We would expect cholesterol and triglyceride levels to be within the health range in someone undertaking athletic training.

  • Liver Function Tests: The liver is a very important organ involved in functions as varied as digestion and the immune response. It is also susceptible to damage by the build-up of fat within it (fatty liver disease). An abnormal liver function test may indicate fatty liver disease and the need to change diet or exercise levels to combat this.

  • Full Blood Count: The haematocrit level, which measures the proportion of red blood cells in the blood, is particularly important. Higher haematocrit levels indicate better oxygen transport capacity, a key factor for athletic performance.

  • Kidney Function Tests: Athletes with high muscle mass and high protein diets may have elevated creatinine levels, potentially causing an artificially low eGFR. A low eGFR may, in this not indicate a problem, but should be followed-up.

Nutritional Status

For the body to perform at its best it needs to be well nourished. There are a range of micronutrients that can be tested for with blood tests to ensure that levels are adequate to support intense training.


Ferritin is a surrogate marker of iron levels in the body. An athlete should be iron-replete to manufacture the red blood cells that are required to transport oxygen around the body. Both vitamin B12 and folate are also required for blood production and athletes may want to check levels of these. Vitamin B12 is also thought to improve recovery after training and it is necessary for energy production within the cells of the body.


Vitamin D is very important for the health of bones, joints and muscles. Vitamin D is made in the body in response to sunshine and therefore low vitamin D levels are extremely common in the UK. Athletes should ensure that they are vitamin D-replete to get the best results.

Running track

Hormone Tests

Testosterone is very important for the development and maintenance of muscle mass and overall athletic performance (it is for this reason that some athletes will illegally inject testosterone or ‘steroids’ to gain an unfair advantage).


Exercise boosts testosterone naturally so we would expect highly athletic individuals to have levels of testosterone at the high end of the normal range. Certainly, low levels of testosterone will be a barrier to achieving athletic potential.

Monitoring Overtraining

Some athletes choose to check for overtraining by monitoring their testosterone/cortisol ratio. Cortisol is a hormone produced by the body in response to stress. There is no specific normal range or cut-off for the ratio between these hormones, but if levels drop by about 30% this is considered to be a sign of overtraining and should prompt a reassessment of a training regime that may be doing more harm than good.

Creatinine kinase is a biomarker that is released when muscles are damaged. Levels of this rise after exercise, often in association with the muscle aches familiar to athletes after training. It can take a week or more for levels to return to normal after intense training. If levels remain high and an athlete continues to push through the pain and discomfort, then they risk doing more damage. Persistently high creatinine kinase levels may be a sign of overtraining and the need to incorporate structured rest into a training regime.

Man checking his watch

Monitoring Athleticism With One Day Tests

Athleticism encompasses various factors, and while performance is the primary indicator, blood tests play a crucial role in optimising an athlete’s health and performance. By understanding and monitoring these health markers, athletes can ensure they are training effectively and maintaining optimal health.

Basic Markers of Health for Athletes

Frequently Asked Questions

What blood tests are done for fitness levels?

There are no specific blood tests for fitness levels but we would expect a fit person to have healthy blood sugar levels, healthy cholesterol levels and no evidence of fatty liver disease. We would also suggest checking that micronutrient levels are adequate to support training and there are blood tests, such as the testosterone/cortisol ratio, that can assess for overtraining. 

What blood tests should athletes do?

Athletes should consider checking micronutrient levels and testosterone levels as well as a range of basic health checks to make sure they are in good health.

Do athletes have high blood urea?

Urea is a breakdown product of protein. Athletes on a high-protein diet may have elevated levels of urea. High urea can also result from dehydration.

Does creatine cause high urea?

High creatinine does not cause high urea but both may be elevated together as both are produced by the breakdown of muscle and processed by the kidneys. 

What blood tests do bodybuilders do?

If bodybuilders are injecting testosterone they usually monitor for the harmful effects of this practice. Other than checking for testosterone levels, this usually involves checking that the liver is not being damaged, that the body is not overproducing red blood cells (which can cause heart attacks and stroke), and sometimes PSA is checked (a tumour marker for prostate cancer) as prostate cancer can be stimulated by high levels of testosterone.

Do fit people age slower?

Evidence suggests that regular exercise slows the ageing process and maintains a longer period of healthy life.

What blood tests are needed for the gym?

No blood tests are needed for the gym, but people undertaking intense training regimes may want to check for their general state of health including cholesterol and blood sugar levels, their micronutrient levels, and their testosterone levels.

Can you get fit after 40?

Yes, fitness can be improved at any age.

Why is nutrition important to physical health?

Without adequate nutrition, both in terms of macronutrients like carbohydrates and protein and micronutrients like iron and vitamin B12, the body simply cannot function. Nutrition is the fuel for all of the body’s processes.

How do I increase my athleticism?

You increase your athleticism by undertaking regular exercise alongside a healthy diet.

Is there a blood test for athleticism?

There is no specific blood test for athleticism but people undertaking intense training regimes may want to check for their general state of health including cholesterol and blood sugar levels, their micronutrient levels, and their testosterone levels.

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