Nutrient

25-Hydroxy Vitamin D [25(OH)D] is the primary circulating form of vitamin D and the best measure of overall vitamin D status. Vitamin D is crucial for calcium absorption, bone health, immune function, and cellular regulation. Deficiency is widespread and linked to various health issues.

Vitamin B12 (Cobalamin) is essential for DNA synthesis, red blood cell formation, neurological function, and methylation processes. Deficiency can lead to megaloblastic anemia, neurological damage (numbness, balance problems, cognitive impairment), and elevated homocysteine and MMA. Serum B12 reflects recent intake and circulating levels, but may not perfectly represent tissue stores, especially in the lower end of the normal range. Optimal levels for neurological health are often considered significantly higher than the lower limit of standard lab ranges (e.g., >400-500 pg/mL). Functional markers like MMA and homocysteine can help confirm status if serum B12 is borderline.

Serum Folate (Vitamin B9) measures the level of folate circulating in the blood. Folate is crucial for DNA synthesis and repair, red blood cell production, and methylation reactions (working with B12). Deficiency causes megaloblastic anemia and elevated homocysteine, and is critical to prevent during pregnancy to avoid neural tube defects. Serum folate reflects recent intake. RBC Folate is a better marker of long-term stores. Optimal serum levels are generally well above the deficiency threshold (e.g., >10-15 ng/mL).

Ferritin is the most sensitive test for iron stores in the body, but it can also be elevated during inflammation, which can mask iron deficiency. Use our Iron Status Interpreter for a comprehensive assessment of your iron levels.