What standard blood tests are recommended for a generally healthy adult who follows a vegetarian diet?

Recommended Blood Work for Vegetarians

For generally healthy adult vegetarians, routine monitoring should include vitamin B12, complete blood count with iron studies (ferritin, hemoglobin), and vitamin D levels, with additional consideration for zinc, calcium, and selenium depending on dietary patterns.

Essential Laboratory Tests

Vitamin B12 (Cobalamin) - Highest Priority

• Vitamin B12 deficiency affects 11-90% of vegetarians depending on age and dietary strictness, with vegans showing deficiency rates of 62% in pregnant women and 25-86% in children 1
• Standard serum B12 measurement should be performed, though methylmalonic acid (MMA) and holotranscobalamin (holoTC) provide greater sensitivity for detecting deficiency, particularly in older adults 2
• B12 deficiency risk exists even in lacto-vegetarians, not just vegans, with 5-10% of the general population consuming below recommended levels 3
• The UK RNI of 1.5 µg/day is notably lower than European recommendations (4 µg/day from EFSA), and studies suggest 4-7 µg/day may be needed to normalize all functional markers 2

Iron Studies

• Complete blood count with serum ferritin is essential, as vegetarian diets contain only non-heme iron which has 2-3 times lower absorption than heme iron from animal sources 2
• Iron bioavailability in vegetarian diets can be enhanced by vitamin C and inhibited by polyphenols, tannins, phytates, and calcium 2
• Premenopausal women require particular attention due to menstrual losses (additional 0.3-0.5 mg daily requirement) and should have hemoglobin and ferritin monitored regularly 4
• Consider iron supplementation when dietary modifications alone don't correct deficiency 4

Additional Micronutrients Based on Dietary Pattern

For Lacto-Vegetarians:

• Vitamin D levels (particularly if limited dairy intake or sun exposure)
• Zinc status (though deficiency less common than in vegans)
• Consider calcium if dairy intake is suboptimal 2

For Vegans (Higher Risk Profile):

• Vitamin B2 (riboflavin) and niacin (B3) - commonly low in vegan diets 5
• Calcium - majority of vegans consume below 750 mg/day recommendation 5
• Zinc and selenium - significantly lower intakes documented 2, 5
• Iodine - at risk without fortified foods or supplements 5
• Vitamin D - essential as no dietary animal sources 2

Monitoring Frequency and Approach

• Initial assessment upon adopting vegetarian diet should include complete metabolic panel, CBC, ferritin, B12, and vitamin D 4
• Annual monitoring for most stable vegetarians following the pattern long-term 4
• More frequent monitoring (every 3-6 months) during first year of dietary transition, in pregnancy, adolescence, or if symptoms develop 4, 6
• Recheck hemoglobin and ferritin every 3 months for first year if iron deficiency was treated, then annually 6

Clinical Considerations and Pitfalls

Common Deficiency Patterns

• Protein intake is generally adequate in Western vegetarians (63-80 g/day exceeds RDA), though vegans consume less than omnivores 2
• Vitamins A, B1, B6, C, E, iron, phosphorus, magnesium, copper, and folate are typically not deficient in well-planned vegetarian diets 5
• Neurological symptoms from B12 deficiency may precede hematological changes (macrocytic anemia), and about one-third of B12 deficiency cases present without anemia 2

Risk Factors Requiring Closer Monitoring

• Lifelong vegetarians have higher deficiency rates than those who adopted the diet later 1
• Elderly vegetarians, particularly sedentary women, face increased risk of inadequate protein and micronutrient intake 2
• Adolescents show lower adherence and require closer follow-up 4
• Pregnancy and lactation increase requirements substantially 1

Supplementation Guidance

• B12 supplementation is essentially mandatory for all vegetarians, as dietary sources are unreliable without fortified foods 7, 8
• Fortified plant-based milk (preferably soy) and appropriate micronutrient supplementation should be encouraged 2
• Iron supplementation (ferrous sulfate 200 mg daily) when deficiency documented, taken with vitamin C for enhanced absorption 6

The evidence strongly supports that vegetarian diets can be nutritionally adequate when appropriately planned 7, 8, but proactive monitoring prevents the development of clinically significant deficiencies that could impact morbidity and quality of life.