Blood tests on a vegan or vegetarian diet
For people who eat a vegan, vegetarian or mostly plant-based diet and want to keep an eye on the nutrients these diets can run low in.
10 tests explainedAI-verified against cited sources. Awaiting expert reviewLast reviewed 2026-10-19
The Academy of Nutrition and Dietetics says well-planned vegetarian and vegan diets are healthful and nutritionally adequate, and a few nutrients are still worth watching. B12 is the main one, since plant foods don't contain it. Iron stores, zinc and the long-chain omega-3s EPA and DHA tend to be lower, and vitamin D depends on sun and fortified foods or supplements. A B12 level on its own can miss an early shortage, so clinicians often add MMA or active B12.
The tests that matter most
Most important first. Each one links to its full page, where the note for this group sits near the top.
Vitamin B12 (Cobalamin)
B12 isn't found in plant foods, and the Academy notes that vegans without fortified foods or supplements can become deficient. A total B12 level is a weak guide on its own, a 2016 review found, so it is often read with MMA or active B12.
Sources: Academy of Nutrition and Dietetics (2016) and Nutrients (2016)
- Usual adult range
- 232–1,245 pg/mL
Methylmalonic Acid (MMA), Serum
MMA builds up when cells don't get enough usable B12. The Academy lists it with serum B12 and holotranscobalamin as the lab tests for B12 status, and a review of B12 in vegetarians found such functional markers give more detail than B12 alone.
Sources: Academy of Nutrition and Dietetics (2016) and Nutrients (2016)
- 60–79
- 69–390 nmol/L
- 80+
- 85–423 nmol/L
Active Vitamin B12 (Holotranscobalamin)
Active B12 (holotranscobalamin) is the part of B12 ready for cells to use. A 2016 review of B12 in vegetarians found it a more useful marker than total B12, though birth control pills and kidney or liver disease can affect it. The Academy lists it among the tests for B12 status.
Sources: Nutrients (2016) and Academy of Nutrition and Dietetics (2016)
Homocysteine
The Academy notes that a mild, early B12 shortage raises homocysteine, often before any symptoms. It is read together with B12 and MMA rather than on its own.
Sources: Academy of Nutrition and Dietetics (2016) and Nutrients (2016)
- 18–60
- up to 14.5 µmol/L
- 61–70
- up to 17.2 µmol/L
Ferritin
Vegetarians eat about as much iron as meat-eaters, but their iron stores (ferritin) are usually lower, the Academy notes. The body absorbs more iron from plant foods when stores are low.
- Men, 20–59
- 30–400 ng/mL
- Men, 60+
- 31–409 ng/mL
Hemoglobin
In Western vegetarians, hemoglobin and most other iron measures are similar to those of meat-eaters, according to the Academy, because iron absorption adapts. Hemoglobin shows whether lower iron stores have gone on to cause anemia.
- Men, 16+
- 13–17.7 g/dL
- Women, 16+
- 11.1–15.9 g/dL
Vitamin D (25-Hydroxy)
Vitamin D status depends on sun exposure and on fortified foods or supplements, the Academy notes. How much the skin makes varies with season, latitude, time of day, skin color, sunscreen and clothing.
- Usual adult range
- 30–100 ng/mL
Zinc
Adult vegetarians tend to have similar or somewhat lower zinc intake and lower blood zinc that is usually still within the usual range, the Academy notes. No health problems from this have been seen in adult vegetarians.
- Usual adult range
- 60–106 µg/dL
Omega-3 Index (EPA+DHA)
Vegetarians eat less EPA and DHA, and vegans usually get almost none from food, so blood and tissue levels can be lower than in meat-eaters. The Academy notes that what this means for health is unknown.
Folate (Vitamin B9), Serum
Plant-rich diets are high in folate, and a 2016 review notes that blood folate tends to be high in vegetarians. Folate can correct the blood-count signs of low B12 but not its effects on nerves, the Institute of Medicine notes, which is why B12 is checked on its own.
Sources: Nutrients (2016) and Institute of Medicine (1998)
- Usual adult range
- 3 and above ng/mL
Ranges shown are the usual adult ranges labs print. The range on your own report is the one your result is judged against.
Getting results you can compare
- A low-normal B12 can still go with a shortage, a 2016 review notes. The Academy lists MMA and active B12 (holotranscobalamin) alongside B12 as tests of B12 status, and the review found they add detail.
Sources: Academy of Nutrition and Dietetics (2016) and Nutrients (2016)
- Season affects how much vitamin D your skin makes, so comparing results from the same time of year makes changes easier to read.
- KDIGO 2024 lists vegetarian and low-protein diets among the things that change creatinine apart from the kidneys, which can shift a creatinine-based eGFR. Your clinician can take your diet into account.
Source: KDIGO (2024)
Good to know
- A normal CBC (complete blood count) doesn't rule out low B12. Folate can correct the blood-count changes of low B12 but not the nerve problems it can cause, the Institute of Medicine notes, and its concern is mainly large amounts of folic acid from supplements. A 2016 review adds that a folate-rich vegetarian diet may hide those blood-count signs too. CDC notes that the recommended amount of folic acid, such as from fortified foods, does not delay finding B12 deficiency.
Sources: Institute of Medicine (1998), Nutrients (2016) and CDC (2026)
- Lower iron stores aren't always a problem. The Academy notes that higher ferritin has been linked to metabolic syndrome, so vegetarians' lower iron stores may even be an advantage. Your clinician can say whether a ferritin result is low enough to matter.
Questions you could ask
- Would MMA or active B12 add anything to my B12 result?
- How often should we check my B12, ferritin and vitamin D?
- Is my ferritin low enough to matter, given my hemoglobin?
- Does my diet change how you read my creatinine or eGFR?
Sources
- Position of the Academy of Nutrition and Dietetics: Vegetarian Diets, Academy of Nutrition and Dietetics (2016)
- Vitamin B12 among Vegetarians: Status, Assessment and Supplementation, Nutrients (2016)
- Folic Acid Safety, Interactions, and Health Outcomes, CDC (2026)
- KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease, KDIGO (2024)
- Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline: Folate, Institute of Medicine (1998)
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-19. How we build and check these pages.
Educational information, not medical advice. Blood Test Tracker doesn’t diagnose or treat, and it doesn’t replace your clinician. Talk with your clinician before changing medications, supplements or care.