Which Blood Tests Does a Vegetarian Need?

If you eat few animal products, it's a good idea to monitor certain nutrient levels

Which Blood Tests Does a Vegetarian Need?
Young women on a vegan or vegetarian diet could benefit from iron supplementation to prevent the chances of developing anemia due to low iron levels in the blood. (Photoroyalty/Shutterstock)
Joel Fuhrman

When it comes to you managing your health, an early warning system is a distinct advantage. That’s where blood tests come in: They're an important tool for assessing your overall health, and provide valuable insight into any potential issues that may be developing.

Your health care provider likely orders a standard screening panel at your annual physical. The problem is, these tests may not pick up on some important nutritional deficits that can impact your health.

In addition to the standard tests ordered by your physician, I recommend the following tests for those who follow a nutritarian (plant-based, nutrient-dense) diet. These tests will give you a clearer picture of your overall nutritional status—what I call "nutrient IQ."

Why Do I Need Special Blood Tests?

When following a diet of high-nutrient plant foods, it's important to ensure that you're getting optimal amounts of some vitamins, minerals, and fatty acids that are more available in animal products.
Also, some people, especially those aged 70 and older, require extra protein to maintain adequate IGF-1 levels. Ensuring that risk factors for diabetes and heart disease are at favorable levels is also important.

How Often Do I Need These Tests? 

The recommended schedule would be to have these tests every five years for adults younger than 65, and every three years for those aged 65 and older.

Vitamin B12 and Methylmalonic Acid

Vitamin B12 isn't naturally present in plant foods, and insufficiency is common, especially in those older than age 60, because B12 absorption becomes less efficient as we age.
Vitamin B12 is important for immune function, brain function, red blood cell production, and DNA synthesis.1
In the mitochondria—the power plants that create cellular energy—vitamin B12 is required for the conversion of methylmalonyl-CoA to succinyl-CoA; when B12 levels are low, methylmalonyl-CoA begins to accumulate and enters the blood as methylmalonic acid (MMA). Elevated MMA in the blood indicates insufficient B12.2

Having results for both B12 and MMA is helpful, as a high MMA might indicate a mild deficiency or a developing deficiency if B12 results are on the lower end of the normal range.

Favorable ranges B12: 160–950 pg/mL or 118–701 pmol/L MMA: Normal ranges vary somewhat between different labs. The normal range is approximately < 300 nmol/L, or < 0.3 µmol/L.3,4


Vitamin B12 acts as a coenzyme for methionine synthase, which produces methionine from homocysteine. Deficiency in B12 (or folate) results in the accumulation of homocysteine.2
Elevated homocysteine is also a risk factor for cardiovascular disease. In excess, homocysteine promotes oxidative stress, endothelial dysfunction, and inflammation. Elevated homocysteine has also been linked to a greater risk of dementia.5
Favorable range: < 15 µmol/L


Ferritin is a protein that stores iron. A low ferritin level in the blood indicates iron deficiency. The iron in plant foods is less absorbable than that from animal foods, and some people on a vegan or near-vegan diet, especially women who are pregnant or of childbearing age, may require iron supplementation. Having too much iron can also create health problems.

Favorable ranges Men: 50–336 µg/L Women: 40–307 µg/L

Note: Iron supplementation guidelines based on ferritin concentration are provided in the Personalized Vitamin Advisor and General Supplement Guidelines.

Hemoglobin A1C

Hemoglobin A1c (HbA1C) is an indicator of long-term (about three months) blood glucose levels. The test measures the percentage of hemoglobin in the blood that is glycosylated (attached to a sugar molecule). More glycosylated hemoglobin is formed at higher blood glucose concentration, and it accumulates over the lifetime of the cell.6 A high HbA1c level indicates prediabetes or diabetes.
Favorable range: < 5.7 percent

Vitamin D

The primary source of vitamin D is sunlight, and supplementation is appropriate to ensure year-round vitamin D adequacy and prevent skin damage from excessive sun exposure. Low vitamin D levels are associated with osteoporosis, depression, autoimmune disease, cancer, and diabetes.7 Excessively high vitamin D levels may also be harmful to health.8–12
Favorable range: 30–45 ng/mL or 75–115 nmol/L

Omega-3 Index

The long-chain omega-3 fatty acids DHA and EPA are usually supplied by fatty fish. DHA and EPA are important structural and functional components of brain and retinal cell membranes, and have anti-inflammatory and cardiovascular benefits.13
Studies have linked a low omega-3 index (below approximately 5 percent) with an increased risk of cognitive decline in older adults.14,15 Conversion of alpha-linolenic acid from plant foods to DHA and EPA is limited, and consuming preformed DHA and EPA (preferably from an algae-derived supplement) is the most reliable way to increase omega-3 levels in the blood.16–19 Adequate levels can be confirmed with an omega-3 index test. The omega-3 index is a measure of the percentage of fatty acids in red blood cell (erythrocyte) membranes that are made up of DHA and EPA.
Favorable range: > 5 percent

Insulin-Like Growth Factor 1

This test is for those 75 years old and older. Insulin-like growth factor 1 (IGF-1) is a growth-promoting hormone important during childhood and adolescence. IGF-1 levels peak during our teens and 20s and then decline as we age. In adults, circulating IGF-1 is primarily determined by protein intake; animal protein increases IGF-1 more than plant protein, and dairy protein is the strongest IGF-1 elevator.20,21 A high IGF-1 level is linked to accelerated aging and an increased risk of cancer and premature death.22–26
However, it's possible for IGF-1 to be too low, especially in older adults. Adequate IGF-1 levels are required to maintain bone mass, muscle mass, and brain function.27–29
Favorable range: 100–160 ng/mL

Oxidized LDL or Measured LDL Cholesterol

This test is for those with a history of LDL cholesterol higher than 110 mg/dl.

Elevated low-density lipoprotein (LDL) cholesterol is one of many risk factors for cardiovascular disease. However, oxidized LDL (oxLDL) is a more important marker of disease risk than total LDL, because oxidized LDL is more atherogenic (plaque formation-promoting) than native LDL.

Oxidized LDL also promotes endothelial dysfunction, progression of atherosclerotic plaque, and destabilization of atherosclerotic plaque.30
Measured LDL, also called "direct LDL," measures the concentration of LDL cholesterol in the blood rather than calculating it using measurements of other lipids. Usually, circulating LDL cholesterol is calculated from the measurements of total cholesterol, high-density lipoprotein (HDL) cholesterol, and triglycerides. The results of calculated LDL are less reliable when LDL is low or triglycerides are high.31
Favorable ranges oxLDL: < 60 U/L Measured LDL: < 100 mg/dl
  1. Office of Dietary Supplements, National Institutes of Health. Dietary Supplement Fact Sheet: Vitamin B12 [http://ods.od.nih.gov/factsheets/VitaminB12/]
  2. Hannibal L, Lysne V, Bjorke-Monsen AL, et al. Biomarkers and Algorithms for the Diagnosis of Vitamin B12 Deficiency. Front Mol Biosci 2016, 3:27.
  3. Ganji V, Kafai MR. Population Reference Values for Serum Methylmalonic Acid Concentrations and Its Relationship with Age, Sex, Race-Ethnicity, Supplement Use, Kidney Function and Serum Vitamin B12 in the Post-Folic Acid Fortification Period. Nutrients 2018, 10.
  4. Mineva EM, Sternberg MR, Zhang M, et al. Age-specific reference ranges are needed to interpret serum methylmalonic acid concentrations in the US population. Am J Clin Nutr 2019, 110:158–168.
  5. Moretti R, Caruso P. The Controversial Role of Homocysteine in Neurology: From Labs to Clinical Practice. Int J Mol Sci 2019, 20.
  6. Fayyaz B, Rehman HJ, Minn H. Interpretation of hemoglobin A1C in primary care setting. J Community Hosp Intern Med Perspect 2019, 9:18–21.
  7. Holick MF. Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease. American Journal of Clinical Nutrition 2004, 80:1678S–1688S.
  8. Durup D, Jorgensen HL, Christensen J, et al. A reverse J-shaped association of all-cause mortality with serum 25-hydroxyvitamin D in general practice: the CopD study. J Clin Endocrinol Metab 2012, 97:2644–2652.
  9. Durup D, Jorgensen HL, Christensen J, et al. A reverse J-shaped association between serum 25-hydroxyvitamin D and cardiovascular disease mortality - the CopD-study. J Clin Endocrinol Metab 2015:jc20144551.
  10. Sempos CT, Durazo-Arvizu RA, Dawson-Hughes B, et al. Is there a reverse J-shaped association between 25-hydroxyvitamin D and all-cause mortality? Results from the U.S. nationally representative NHANES. J Clin Endocrinol Metab 2013, 98:3001–3009.
  11. Zittermann A, Iodice S, Pilz S, et al. Vitamin D deficiency and mortality risk in the general population: a meta-analysis of prospective cohort studies. Am J Clin Nutr 2012, 95:91–100.
  12. Zheng YT, Cui QQ, Hong YM, Yao WG. A meta-analysis of high dose, intermittent vitamin D supplementation among older adults. PLoS One 2015, 10:e0115850.
  13. Harris WS, Tintle NL, Imamura F, et al. Blood n-3 fatty acid levels and total and cause-specific mortality from 17 prospective studies. Nature Communications 2021, 12:2329.
  14. Coley N, Raman R, Donohue MC, et al. Defining the Optimal Target Population for Trials of Polyunsaturated Fatty Acid Supplementation Using the Erythrocyte Omega-3 Index: A Step Towards Personalized Prevention of Cognitive Decline? J Nutr Health Aging 2018, 22:982–998.
  15. Lukaschek K, von Schacky C, Kruse J, Ladwig KH. Cognitive Impairment Is Associated with a Low Omega-3 Index in the Elderly: Results from the KORA-Age Study. Dement Geriatr Cogn Disord 2016, 42:236–245.
  16. Craddock JC, Probst YC, Neale EP, Peoples GE. A Cross-Sectional Comparison of the Whole Blood Fatty Acid Profile and Omega-3 Index of Male Vegan and Omnivorous Endurance Athletes. J Am Coll Nutr 2021:1–9.
  17. Sarter B, Kelsey KS, Schwartz TA, Harris WS. Blood docosahexaenoic acid and eicosapentaenoic acid in vegans: Associations with age and gender and effects of an algal-derived omega-3 fatty acid supplement. Clin Nutr 2014.
  18. Office of Dietary Supplements, National Institutes of Health. Omega-3 Fatty Acids. Fact Sheet for Health Professionals [https://ods.od.nih.gov/factsheets/Omega3FattyAcids-HealthProfessional/]
  19. Arterburn LM, Hall EB, Oken H. Distribution, interconversion, and dose response of n-3 fatty acids in humans. Am J Clin Nutr 2006, 83:1467S–1476S.
  20. Thissen JP, Ketelslegers JM, Underwood LE. Nutritional regulation of the insulin-like growth factors. Endocr Rev 1994, 15:80–101.
  21. Clemmons DR, Seek MM, Underwood LE. Supplemental essential amino acids augment the somatomedin-C/insulin-like growth factor I response to refeeding after fasting. Metabolism 1985, 34:391–395.
  22. Chitnis MM, Yuen JS, Protheroe AS, et al. The type 1 insulin-like growth factor receptor pathway. Clin Cancer Res 2008, 14:6364–6370.
  23. Werner H, Bruchim I. The insulin-like growth factor-I receptor as an oncogene. Arch Physiol Biochem 2009, 115:58–71.
  24. Davies M, Gupta S, Goldspink G, Winslet M. The insulin-like growth factor system and colorectal cancer: clinical and experimental evidence. Int J Colorectal Dis 2006, 21:201–208.
  25. Sandhu MS, Dunger DB, Giovannucci EL. Insulin, insulin-like growth factor-I (IGF-I), IGF binding proteins, their biologic interactions, and colorectal cancer. J Natl Cancer Inst 2002, 94:972–980.
  26. Kaaks R. Nutrition, insulin, IGF-1 metabolism and cancer risk: a summary of epidemiological evidence. Novartis Found Symp 2004, 262:247-260; discussion 260–268.
  27. Lamberts SW, van den Beld AW, van der Lely AJ. The endocrinology of aging. Science 1997, 278:419–424.
  28. Doi T, Shimada H, Makizako H, et al. Association of insulin-like growth factor-1 with mild cognitive impairment and slow gait speed. Neurobiol Aging 2015, 36:942–947.
  29. Calvo D, Gunstad J, Miller LA, et al. Higher serum insulin-like growth factor-1 is associated with better cognitive performance in persons with mild cognitive impairment. Psychogeriatrics 2013, 13:170–174.
  30. Gradinaru D, Borsa C, Ionescu C, Prada GI. Oxidized LDL and NO synthesis--Biomarkers of endothelial dysfunction and ageing. Mech Ageing Dev 2015, 151:101–113
  31. Sung KC, Kwon CH, Lee MY, et al. Comparison of Low-Density Lipoprotein Cholesterol Concentrations by Direct Measurement and by Friedewald Calculation. Am J Cardiol 2020, 125:866–873.
Joel Fuhrman, M.D. is a board-certified family physician, seven-time New York Times best-selling author and internationally recognized expert on nutrition and natural healing. He specializes in preventing and reversing disease through nutritional methods.
Related Topics