I Ranked 100 Health Markers (Most People Get These Wrong)

Siim emphasizes that high blood pressure is a 'silent killer' because it has no symptoms, yet it is one of the biggest drivers of heart disease, stroke, and dementia. He notes that BP is highest in the morning and lowest around 6 PM, so measuring at a consistent time is crucial. He warns that a single annual reading at the doctor's office is nearly useless because most people are nervous, which spikes their BP. Instead, he recommends a routine of sitting calmly for 5–15 minutes and measuring at home daily to establish a trend. This allows early detection and intervention before damage accumulates.

Siim places iron and ferritin in the 'vital' tier due to their causal role in heart disease. He explains that iron accumulates with age in men, and high levels damage the endothelium, promoting atherosclerosis. He notes that dietary strategies like consuming polyphenols, fiber, and coffee can chelate some iron, but blood donation is far more effective. He also mentions that there may be additional longevity benefits from blood donation beyond iron removal, though the evidence is still emerging. He advises checking iron status at least annually and acting if levels are above the optimal range.

Siim ranks omega-3 index as vital, citing robust epidemiological data linking higher levels to reduced mortality and multiple chronic diseases. He clarifies that the ratio of omega-6 to omega-3 is less important than the absolute omega-3 index; if omega-3 index is high, a higher omega-6 intake is less concerning. He recommends algal oil as a plant-based alternative that is equally effective as fish oil, and notes that chia seeds or flax may not suffice for those with poor conversion. He advises testing to confirm levels rather than guessing.

Siim distinguishes between muscle mass and muscle strength, noting that while sarcopenia is harmful, excessive muscle mass (bodybuilder levels) may shorten lifespan. He points to gymnasts and calisthenics athletes as having an optimal balance of strength, leanness, and mobility. The proposed benchmarks are achievable for most people with consistent training and represent a threshold beyond which additional strength yields diminishing returns for longevity. He also emphasizes that these lifts should be accompanied by good metabolic health and low visceral fat.

Siim explains that HRV reflects autonomic nervous system balance and is a proxy for recovery and biological age. He notes that commercial devices give widely varying results, so comparing your number to someone else's is meaningless. He shares that his own HRV is 100+, but he knows healthy people stuck at 45 despite doing everything right. The actionable insight is to watch for deviations from your personal baseline: a drop a few days before symptoms can warn of infection, while a long-term downward trend may indicate burnout. He also cautions that a low resting heart rate with low HRV is a red flag, not a sign of fitness.

Siim places V2 max in the vital tier as an umbrella marker of cardiorespiratory fitness and overall health. He notes that while lab-measured V2 max is ideal, the Cooper test is a practical alternative that incorporates actual running ability. He argues that a good Cooper test result guarantees a good V2 max, and both predict lower mortality. He ranks the Cooper test slightly below lab V2 max only because the lab test may capture additional physiological components, but for most people, the Cooper test is sufficient and more accessible.

Siim cites a clinical trial in young healthy males showing that neither testosterone nor DHT predicted muscle mass; androgen receptor density did. He explains that receptors act as 'docks' for testosterone—without enough docks, high circulating hormone has little anabolic effect. Receptor density is highly genetic but can be upregulated by resistance training (especially high volume), creatine supplementation, and adequate protein intake. This reframes the goal from chasing high T numbers to optimizing receptor sensitivity through training and nutrition. He also notes that very high testosterone (e.g., from anabolic steroids) does not protect against heart disease and may even shorten maximum lifespan, so the sweet spot for longevity is moderate, not supraphysiological.

Siim explains that these tests show massive intra-individual variability: results change depending on whether you're fasted, the time of day, recent exercise, or subclinical infections. He references an experiment by Matt Kaeberlein who took four different tests at the same time and got four different results, some differing by several years. Because you can never know the 'optimal' testing condition, the number you get is meaningless. Even if it says you're five years younger, you won't change your behavior—you'll just keep doing what you're doing. The DunedinPACE test, while slightly better, still suffers from inherent noise due to the dynamic nature of aging. He contrasts this with phenotypic age, which at least uses standard blood markers that can be individually addressed.

Siim uses himself as an example: BMI 25.5 but 10% body fat, low visceral fat, excellent metabolic health. He cautions that someone with a BMI of 31 claiming it's all muscle is likely still carrying excess body fat—to reach that BMI with leanness would require being a 'mass monster' on anabolic steroids, which is itself unhealthy. He concludes that BMI has some validity at extremes (if your BMI is 31, you're probably overfat or unnaturally huge), but for most people between 25–27, it may simply reflect above-average muscle mass. He recommends looking at waist-to-hip ratio, visceral fat, and metabolic markers instead.

Siim explains that uric acid acts as an antioxidant in the body, so moderately low levels may be protective, but excessively low levels (e.g., from over-supplementation or extreme diets) could impair defense against oxidative stress, potentially contributing to neurodegeneration. He references associations between low uric acid and dementia. He also notes that exercise can transiently raise uric acid, so a single high reading in an active person isn't necessarily alarming. The key is to stay within the reference range and interpret in context of other inflammatory markers.

Siim cites clinical trials where niacin raised HDL but failed to lower heart attack risk, indicating HDL is not causal. He explains that HDL's primary value is as a biomarker: low HDL often signals insulin resistance or metabolic syndrome, while high HDL generally reflects good metabolic health. However, he warns that HDL particles can become oxidized in a high-inflammation, high-oxidative-stress environment, and oxidized HDL contributes to atherosclerosis just like oxidized LDL. Therefore, the goal is not to artificially inflate HDL but to maintain metabolic health and keep oxidative stress low. He suggests a sweet spot of 40–80 mg/dL.