The 10 Blood Markers Worth Knowing (And What I Do About Mine)

I got my first full blood panel at twenty-five, after four years of college baseball spent assuming I was fine because I was young and I could still lift. A few things were not where I thought they were. Fixing them did more for how I feel day to day than any program change I have ever made.

Here is the thing nobody tells you: a mirror and a scale measure two things, and neither of them is how well your body is running. You can be lean and strong and still be low on iron, short on vitamin D, and carrying inflammation you cannot feel yet.

These are the ten I pay attention to. I am a coach, not a doctor, so treat this as a list of things worth asking about rather than anything to act on alone.

1. Vitamin D

The one almost everyone is low on, and the one with the widest reach. It is involved in bone health, muscle function, and immune function. If you live somewhere with a real winter, work indoors, or both, assume you are low until a test says otherwise. Mine was low the first time I checked and I live in Minnesota, which surprised exactly nobody.

2. Ferritin (and iron)

Ferritin is your stored iron. It is the marker that gets missed most often, and low stores show up as being tired in a way that sleep does not fix, and as training that feels harder than it should for no obvious reason. Worth checking for anyone, and especially worth checking if you menstruate, because the losses are real and monthly.

3. Magnesium (RBC)

Ask for red blood cell magnesium rather than serum magnesium if you can — serum is tightly regulated and can look normal while stores are not. Magnesium is involved in muscle function, nerve function and sleep quality. It is also one of the easiest gaps to close.

4. A full thyroid panel

Not just TSH. A full panel looks at free T3, free T4, and antibodies as well. Thyroid function sets the pace of your metabolism, which means it touches energy, body composition, temperature regulation and mood. A single TSH number in isolation can miss a lot of the picture.

5. Hemoglobin A1c

A rolling three-month average of your blood sugar. This one matters even if you are lean, because it reflects how your body has actually been handling carbohydrate over time rather than how it handled breakfast. It is one of the better long-run signals on the whole panel.

6. hs-CRP

A sensitive marker of general inflammation. It moves for a lot of reasons — a recent illness, a brutal training block, poor sleep, a rough couple of months. On its own it does not tell you much. Tracked over a year, it tells you a great deal about whether your recovery is keeping up with what you are asking of yourself.

7. A full lipid panel

Total, LDL, HDL, triglycerides, and ideally ApoB. Being young and athletic does not make you exempt here, and this is a slow-moving story where finding out early is worth a lot. Ask your doctor what your numbers mean for you specifically.

8. Hormones, read as a set

For men that means total and free testosterone, estradiol and SHBG. For women it means a panel timed to your cycle. The reason to look is not to chase a number, it is that hormone levels respond to sleep, stress, energy intake and training load, which makes them a useful readout on whether your life is actually sustainable. Anything that comes back off belongs in a conversation with a licensed practitioner, not a group chat.

9. Liver enzymes

ALT and AST. They move for a lot of ordinary reasons, including a heavy training week, which is exactly why you want a baseline. Knowing what yours look like when everything is normal is what makes an abnormal result meaningful later.

10. B12 and folate

Both are involved in red blood cell formation and nerve function. Worth checking generally, and worth checking sooner if you eat little or no animal protein.

What I actually do with this

Twice a year, always in the morning, always fasted, and always when life is normal — not after a month of behaving myself, because that would defeat the point. I write the numbers down. Then I compare them to last time, because the trend is the useful part. A single reading is a snapshot; two readings a year apart is information.

The changes that move these markers are boring, which is the good news. Sleep. Enough food. Enough protein. Sunlight or a supplement in the winter. Training you recover from. I fill gaps with supplements only after a test shows a gap, and I have written up what I actually take if you want the short list.

Disclosure: I’m a Paath ambassador and I earn a commission if you order through the links on those pages, at no extra cost to you. It’s why I keep the list short.

If you want the whole thing done properly, with a practitioner reading every marker and writing you a plan, that is what the labs page covers.

None of this is medical advice, and I am a coach rather than a physician. Nothing here diagnoses or treats anything. Take your results to a licensed practitioner and ask what they mean for you.