I'm not vegan. I should say that upfront so you know where I'm coming from.
I eat meat. Not a huge amount, but I do. My perspective on plant-based diets is simple: I respect the choice, I understand the reasons (ethical, environmental, health-related), and I think the evidence is clear that well-planned vegan and vegetarian diets can support excellent health. The Australian Dietary Guidelines acknowledge this. The research supports it.
But "well-planned" is doing a lot of heavy lifting in that sentence.
I wrote about my colleague Tom in the B12 article. A committed vegan who didn't supplement B12 and developed deficiency with neurological symptoms. His story was the catalyst for this piece. Because after talking to Tom, I started looking at the data, and what I found is that the nutritional gaps in plant-based diets are well-documented, entirely predictable, and almost entirely preventable. But only if you know what to monitor.
The problem isn't the diet. The problem is the monitoring gap. Most vegans and vegetarians I've spoken to know they should supplement B12. Fewer know they should check their iron regularly. Even fewer think about zinc, iodine, or omega-3 DHA/EPA. And almost none are testing to confirm their supplementation is actually working.
There's a paradox here: people who choose plant-based diets are often more health-conscious than average. They research their food choices carefully. They spend more on quality produce. They're thoughtful about what goes into their bodies. And yet, because the diet is perceived as inherently healthy, there's an assumption that testing is less necessary. In reality, it's more necessary.
This article is a practical guide to which blood tests matter on a plant-based diet, what to monitor, how often to test, and how to build a panel that gives you genuine confidence that your diet is working for you.
A note before we get into it
General information only. I'm not a dietitian or a doctor. Nutritional management on a plant-based diet benefits from professional guidance, particularly during pregnancy, breastfeeding, childhood growth, or if you have existing health conditions.
This article isn't anti-vegan. It's pro-information. Your dietary choice is yours. Your blood work is your feedback loop.
Your diet is your choice. Your blood work is your feedback.
I want to set the tone early because this is a sensitive topic. Plant-based communities can feel defensive about nutritional monitoring, as if acknowledging potential deficiencies is an attack on the diet itself. It's not. Every dietary pattern has strengths and limitations. Omnivores are frequently deficient in fibre, vitamin D, and folate. Vegans are frequently deficient in B12, iron, and zinc. Neither pattern is perfect. Both benefit from testing.
The goal isn't to prove that plant-based diets are nutritionally inadequate. The evidence doesn't support that claim. Well-planned plant-based diets are associated with lower rates of cardiovascular disease, type 2 diabetes, certain cancers, and obesity. The goal is to identify which specific nutrients need monitoring so you can supplement intelligently and test to confirm you're on track.
Think of blood testing as the quality control system for your diet. You wouldn't run a business without checking the numbers. Don't run a restrictive diet without checking yours.
Tier 1: Must-test nutrients
These are the nutrients where plant-based diets carry a documented, significant risk of deficiency. Testing isn't optional here. It's part of the dietary strategy.
Vitamin B12
Why it's Tier 1
B12 is found almost exclusively in animal products. There are no reliable, unfortified plant sources. Without supplementation, deficiency in vegans is inevitable. It's only a question of when. Systematic reviews show deficiency rates of 11-86% across vegan populations, with higher rates among those not supplementing.
The risk
B12 deficiency causes megaloblastic anaemia and neurological damage (tingling, numbness, cognitive decline, balance problems). Neurological damage can be irreversible if caught late. High folate intake in vegans can mask the haematological signs while neurological damage progresses silently.
Supplementation
50-100 mcg daily of cyanocobalamin or methylcobalamin, or 2,000 mcg weekly. Fortified foods (nutritional yeast, fortified plant milks) contribute but are rarely sufficient alone. Intake is inconsistent and absorption variable.
Testing frequency: Annually for vegans, biannually for vegetarians.
I covered B12 in depth in the dedicated article, including Tom's story and the folate masking effect.
Test it with Bloody Good:
Product: Vitamin B12 Blood Test
Iron (Ferritin and Iron Studies)
Why it's Tier 1
Plant-based diets provide only non-haem iron, which is absorbed at roughly 2-20% efficiency compared to haem iron from animal sources at 15-35%. Additionally, phytates in whole grains, legumes, and nuts (staples of plant-based diets) bind iron and further reduce absorption.
The nuance
Not all vegans and vegetarians become iron deficient. Some manage very well through dietary planning: vitamin C with iron-rich foods, soaking legumes, avoiding tea or coffee with meals. But the margin for error is smaller, and menstruating women, athletes, and anyone with higher iron demands are at genuine risk.
The key marker
Ferritin. As covered in the iron article, you can have a normal FBC while your ferritin is depleted. Ferritin below 30 mcg/L is considered functionally low by many clinicians, even if it's technically "in range."
Testing frequency: Annually for all plant-based eaters. Every 6 months for menstruating women, athletes, or anyone with a history of low iron.
Test it with Bloody Good:
Vitamin D
Why it's Tier 1
Dietary sources of vitamin D are limited even for omnivores. Oily fish and fortified dairy are the main sources, neither of which features in a vegan diet. Plant-based diets provide negligible dietary vitamin D unless heavily supplemented with fortified foods.
Given that one in four Australians is already vitamin D deficient (as I covered in the vitamin D article), and that sun exposure may not be sufficient (especially in southern states during winter), vegans face a compounded risk: limited dietary sources plus the same sun exposure limitations as everyone else.
Supplementation
Vitamin D3 (cholecalciferol) is the preferred form. Note that most D3 is derived from lanolin (sheep's wool), which some vegans avoid. Vegan D3 from lichen is available. Vitamin D2 (ergocalciferol) is plant-derived but less effective at raising blood levels.
Testing frequency: Annually, ideally at the end of winter when levels are lowest.
Test it with Bloody Good:
Product: Vitamin D (25-OH) Blood Test
Tier 2: Should-test nutrients
These nutrients can be obtained from plant sources, but absorption is often lower and deficiency is more common in plant-based populations than in omnivores.
Zinc
Why it matters
Zinc is involved in immune function, wound healing, DNA synthesis, taste and smell, and over 300 enzymatic reactions. Plant-based diets provide zinc through legumes, nuts, seeds, and whole grains, but phytate binding reduces absorption by up to 50% compared to zinc from animal sources.
The evidence
Systematic reviews consistently show lower zinc status in vegans and vegetarians compared to omnivores. Clinical deficiency isn't always dramatic. It can present as increased infections, slow wound healing, impaired taste, skin changes, or poor immune response.
Practical tip
Soaking, sprouting, and fermenting legumes and grains reduces phytate content and improves zinc availability. But testing confirms whether your dietary strategy is actually working.
Testing frequency: Every 1-2 years, or if symptoms of deficiency are present.
Test it with Bloody Good:
Product: Zinc Blood Test
Iodine
Why it matters
Iodine is critical for thyroid function. Your thyroid needs it to produce T3 and T4. Iodine deficiency re-emerged as a concern in Australia after it was identified in mainland populations (particularly NSW and Victoria) in the mid-2000s. Mandatory iodine fortification of bread was introduced in 2009, which has improved population status. But vegans who avoid conventional bread or rely on non-iodised salt may still be at risk.
Plant-based sources
Seaweed (variable and sometimes excessively high, so use cautiously), iodised salt, some fortified plant milks. The intake is often inconsistent.
The thyroid connection
If you're vegan and your thyroid results are borderline (as I covered in the thyroid article), iodine status is worth checking before assuming the thyroid is the primary problem.
Testing: Urinary iodine is the standard population measure, but it's variable day to day. Thyroid function (TSH) is a practical indirect marker. If your thyroid function is normal, your iodine status is likely adequate.
Test it with Bloody Good:
Omega-3 (DHA/EPA)
Why it matters
The omega-3 fatty acids DHA and EPA are important for brain function, cardiovascular health, and anti-inflammatory processes. Plant sources provide ALA (alpha-linolenic acid), which the body can convert to DHA and EPA, but conversion rates are very low (typically less than 5-10% for EPA and less than 1% for DHA).
The practical reality
Most vegans have significantly lower blood levels of DHA and EPA than fish-eating populations. Whether this translates to clinically meaningful health differences is still debated. But for people concerned about cognitive function, cardiovascular protection, or inflammation, supplementation with algal DHA/EPA (derived from microalgae, fully vegan) is the most reliable approach.
Testing: Omega-3 index testing is available but not part of standard blood panels. Consider it if omega-3 status is a specific concern.
Tier 3: Usually adequate on a well-planned plant-based diet
These nutrients are generally well-covered by plant-based diets and don't require routine monitoring unless there's a clinical reason.
Folate (vitamin B9): Plant-based diets are typically rich in folate from leafy greens, legumes, and fortified foods. Deficiency is uncommon. In fact, high folate is the norm in vegans, which is part of why B12 deficiency gets masked.
Vitamin C: Abundant in fruits and vegetables. Deficiency is very rare on any diet that includes fresh produce.
Fibre: Plant-based diets are generally fibre-rich, often significantly higher than omnivorous diets. This is one of the clear dietary advantages.
Magnesium: Found in nuts, seeds, legumes, and whole grains. Intake is usually adequate or even above average in plant-based eaters.
Potassium: Typically well-covered through fruits, vegetables, and legumes.
Protein: Adequate protein intake is achievable on a well-planned plant-based diet, though total intake is typically lower than in omnivores. Combining different plant protein sources (grains and legumes) ensures complete amino acid profiles. Testing isn't routinely needed unless there's a specific concern about protein status.
The "I supplement everything" assumption
Tom's story from the B12 article is the perfect illustration of why this assumption is dangerous.
He ate nutritional yeast. He drank fortified soy milk. He thought he was covered. His B12 was 112 pmol/L.
The gap between "I take supplements" and "my levels are adequate" is a gap that only blood testing can close. Here's why.
Supplementation doesn't guarantee absorption. GI health, medication interactions (metformin, PPIs), supplement quality, timing, and individual variation all affect how much of what you swallow actually reaches your bloodstream.
Fortified food intake is inconsistent. You might eat nutritional yeast three times one week and not at all the next. Fortification levels vary between brands. The amount of B12 or vitamin D in a serving of fortified plant milk is modest, and skipping a day matters more than most people realise.
Dosing may be wrong. Over-the-counter supplement doses vary enormously. Some multivitamins contain inadequate B12 for a vegan. Some contain excessive vitamin A. Without testing, you don't know whether your specific combination is doing the job.
You can't feel most deficiencies until they're advanced. B12 stores can last 3-5 years before symptoms appear. Iron depletion progresses silently. Vitamin D deficiency is asymptomatic in most people. By the time you feel something, you've been deficient for months or years.
Testing isn't a lack of trust in your diet. It's a verification system. And for a diet that requires supplementation to be nutritionally complete (which veganism does, and that's simply a factual statement, not a criticism), verification isn't optional.
How often to test
Minimum recommended schedule for vegans:
| Test | Frequency |
|---|---|
| Vitamin B12 | Annually |
| Iron Studies (Ferritin) | Annually (6-monthly for menstruating women) |
| Vitamin D | Annually (end of winter ideally) |
| Zinc | Every 1-2 years |
| Full Blood Count | Annually |
| Thyroid Function (TSH) | Every 2 years (annually if iodine intake uncertain) |
| Folate | Every 2 years (mainly to assess alongside B12) |
For vegetarians: Same panel, but iron and B12 testing can be biannual if prior results have been consistently adequate and supplementation is stable.
Additional testing in specific situations:
Planning pregnancy: Add homocysteine, iodine, full thyroid panel.
Athletes: Add FBC, ferritin every 6 months, CRP.
Over 50: Add HbA1c, cholesterol, kidney function.
How to prepare for testing
Fast for 8-12 hours if including iron studies (recommended for most plant-based panels). Water is fine.
Stop B12 supplements 7 days before to get an accurate baseline. Continue other supplements unless your clinician advises otherwise.
Stop iron supplements 24-48 hours before.
Stop biotin supplements 48-72 hours before (biotin interferes with thyroid and some hormone assays, and it's commonly found in hair/skin/nail supplements).
Test in the morning for the most consistent results, especially if including iron studies.
Building your plant-based blood panel
Here's how to construct a vegan or vegetarian panel using Bloody Good's tests.
The essential vegan panel (Tier 1, test annually)
Vitamin B12 Blood Test - non-negotiable for vegans.
Iron Studies (Including Ferritin) - non-haem iron absorption is lower; ferritin is the key marker.
Vitamin D (25-OH) - limited dietary sources on plant-based diets.
Full Blood Count (FBC) - screens for anaemia and immune markers.
Folate Blood Test - context alongside B12 (folate masking).
Extended plant-based panel (Tier 2, test every 1-2 years)
Zinc Blood Test - phytate reduces absorption from plant sources.
Thyroid Function Test (TFT) - indirect marker of iodine adequacy plus thyroid screening.
Homocysteine Blood Test - functional marker of B12 and folate status plus cardiovascular risk.
Additional context (situational)
HbA1c - metabolic health screening (relevant for all adults).
Cholesterol (Lipid Studies inc. HDL) - cardiovascular baseline.
Calcium Blood Test - if dairy is excluded entirely and calcium supplementation is inconsistent.
If you want broad coverage, The Bloody Good Test covers 100 biomarkers including B12, iron studies, vitamin D, FBC, folate, thyroid, cholesterol, liver, kidney, HbA1c, and more. Adding the zinc test separately gives you nearly complete coverage of the plant-based nutrient risk profile in two orders.
What to do with your results
If everything's adequate: Confirmation that your supplementation strategy and dietary planning are working. Keep going. Retest annually to confirm it stays that way.
If B12 is low: Start or increase supplementation immediately. If neurological symptoms are present, see your GP. Intramuscular injections may be needed for faster repletion. Retest at 3 months.
If iron/ferritin is low: Review dietary iron sources and absorption strategies (vitamin C with meals, reduce phytate exposure). Consider supplementation under GP guidance. For severe depletion, iron infusion may be appropriate. Retest at 3 months.
If vitamin D is low: Supplement with vitamin D3 (vegan D3 from lichen is available). Standard dose 1,000-2,000 IU daily for mild deficiency. Retest at 3 months.
If zinc is low: Increase zinc-rich foods (pumpkin seeds, hemp seeds, cashews, chickpeas) and consider supplementation. Zinc competes with iron for absorption, so take them at different times if supplementing both.
If multiple deficiencies are present: This is common and suggests the overall supplementation strategy needs a review. Consider working with a dietitian experienced in plant-based nutrition to build a more structured plan. Testing without a plan is just data. Testing with a plan is health management.
If everything's fine and you feel great: That's the goal. You've proven your dietary pattern is nutritionally complete with appropriate supplementation. Keep testing annually to stay on track, because the variables change (seasons, stress, supplement brand changes, life stage transitions).
Explore more biomarkers
Browse the Bloody Good Biomarker Directory
General information only. This article is not medical advice and is not a substitute for care from a qualified health professional. If you have concerning symptoms or urgent health issues, seek medical attention promptly.