On blood work reports, ironically the “normal range” column is technically not about what is normal or abnormal. It only represents a distribution of values within which 95% of the population falls. Falling anywhere within that entire range does not mean it is necessarily what is considered ideal and being outside that range does not automatically mean there is a concern. Individuals vary, and what's most important is not just the number on the test but how it fits into the broader picture of your health.
Optimal is where the greatest longevity and lowest risk of diseases happens for you. Optimal is where people feel and function the best. For some blood work values this means right at the middle of the range, for others it could be at the high end or low end. The risks and benefits from one level to the next within that range can be drastically different. The ideal level can be different based on your age, gender, ethnicity, and other health conditions.
These ideal levels are not often readily available or individualized to the person, so at our clinic we look at hundreds of studies done in specific contexts on thousands and sometimes millions of people and the impact on the risk of various diseases and longevity.
National Health Service in London, UK: https://pubmed.ncbi.nlm.nih.gov/30425140/
Whyte MB, Kelly P. The normal range: it is not normal and it is not a range. Postgrad Med J. 2018 Nov;94(1117):613-616. doi: 10.1136/postgradmedj-2018-135983. Epub 2018 Nov 13. PMID: 30425140; PMCID: PMC6352401.