Vegan Nutritional Deficiencies: The Watch List

A planned vegan diet meets the nutritional needs of healthy adults across all life stages per the Academy of Nutrition and Dietetics’ 2016 position. Deficiencies on a vegan diet typically arise from one of three patterns: insufficient calorie intake, inadequate variety, or skipping key supplementation. The eight nutrients below are the ones most commonly out of range when vegan diets are unplanned. This guide covers each nutrient’s role, signs of deficiency, blood tests to consider, supplementation thresholds, and how to address each issue. Disclaimer: this is general nutrition information; suspected deficiencies should be evaluated by a healthcare provider.

The watch list at a glance

Nutrient	Risk on unplanned vegan diet	Standard answer
Vitamin B12	High (no plant source)	Mandatory supplement
Vitamin D	Moderate (universal issue)	Supplement, especially in winter
Iron	Moderate (lower bioavailability)	Diet + vitamin C pairing; test ferritin
Calcium	Moderate (intentional sourcing required)	Fortified milks + tofu + greens
Omega-3 EPA/DHA	Moderate (poor ALA conversion)	Algae oil supplement
Iodine	Moderate (low in plant foods)	Iodised salt or supplement
Zinc	Lower (phytate consideration)	Pumpkin seeds + legumes; multivitamin
Choline	Lower (often under-tracked)	Soybeans, tofu, broccoli; supplement if pregnant

1. Vitamin B12

Risk level: High. There is no reliable plant-food source of bioavailable B12.

Function: Red blood cell formation, neurological function, DNA synthesis.

Signs of deficiency:

Persistent fatigue
“Brain fog,” cognitive sluggishness
Tingling or numbness in hands/feet
Glossitis (red, smooth tongue)
Pallor
Mild depression
Macrocytic anaemia (later stage)
Neurological symptoms — irreversible if very advanced

Tests:

Serum B12 (>200 pg/mL adequate; many practitioners prefer >400)
Methylmalonic acid (MMA) — more sensitive
Homocysteine — secondary marker

Action:

Supplement: 25–100 mcg daily, OR 1000 mcg twice weekly, OR 2500 mcg once weekly
Methylcobalamin or cyanocobalamin both work
See vegan B12 complete guide

Threshold for testing: All vegans 6–12 months in (baseline). Re-test every 2–3 years if supplementing consistently.

2. Vitamin D

Risk level: Moderate. Universal issue (most populations are insufficient regardless of diet); vegans don’t have additional risk factors beyond non-vegans.

Function: Calcium absorption, immune function, mood regulation.

Signs of deficiency:

Fatigue
Bone or joint pain
Frequent illness
Hair thinning
Mood disturbances (some evidence)

Tests:

Serum 25(OH)D
Adequate range: 30–80 ng/mL (75–200 nmol/L) per most guidelines

Action:

Supplement: 600–2000 IU daily depending on baseline + sun exposure
Vegan-friendly forms: D2 (ergocalciferol; non-animal) or D3 derived from lichen
Test mid-winter if at high latitude; supplement as needed

Threshold for testing: Anyone with persistent fatigue, frequent illness, or living at high latitude in winter.

3. Iron

Risk level: Moderate. Plant iron is non-heme; bioavailability is lower than heme iron, but adequate with intentional planning.

Function: Oxygen transport (haemoglobin), enzyme co-factor.

Signs of deficiency:

Persistent fatigue
Pallor
Reduced exercise tolerance
Cold extremities
Restless legs
Brittle nails, hair loss
Microcytic anaemia (late)

Tests:

Ferritin (storage iron; most sensitive early indicator)
<15 ng/mL deficient; <30 low; 30–100 adequate
Full iron panel if ferritin abnormal

Action:

Pair iron-rich meals with vitamin C
Avoid tea/coffee within 1 hour of iron-rich meals
Supplement guided by ferritin testing
Standalone iron supplements (ferrous sulfate, ferrous bisglycinate) starting 30–60 mg elemental iron if deficient
See vegan iron foods and absorption

Threshold for testing: Premenopausal women annually; athletes annually; symptomatic individuals; anyone with restrictive eating or 6–12 months into a vegan diet.

4. Calcium

Risk level: Moderate. Fully addressable with intentional sourcing; commonly under-consumed when dairy is replaced with non-fortified alternatives.

Function: Bone mineralisation, muscle contraction, nerve transmission, blood clotting.

Signs of deficiency:

Often subclinical for years (bone density loss)
Late: increased fracture risk, dental issues
Severe (rare): tetany, muscle cramps

Tests:

Serum calcium (often normal even with low intake; the body maintains blood calcium by drawing from bones)
DEXA scan for bone density (especially over age 50 or with other risk factors)
Vitamin D status as supporting marker

Action:

Fortified plant milks (300–450 mg per cup)
Calcium-set tofu (250–800 mg per ½ cup)
Leafy greens (collard, kale, bok choy)
Aim for 1000 mg/day adult; 1200 mg/day for postmenopausal women and over-70s
Supplement only if dietary intake consistently low (max 500 mg per dose)
See vegan calcium complete guide

Threshold for testing: DEXA scan after age 50, especially if other risk factors.

5. Omega-3 EPA/DHA

Risk level: Moderate. ALA-to-EPA/DHA conversion is poor (5–10%); algae oil is the reliable source.

Function: Cardiovascular health, neurological function, anti-inflammatory effects.

Signs of deficiency:

Often subclinical (no overt deficiency syndrome in adults)
Possible: dry skin, eczema, mood disturbances, joint stiffness
Pregnancy: possible adverse fetal neurodevelopmental outcomes

Tests:

Omega-3 Index blood test (specialised; not routine)
Most clinicians don’t routinely test omega-3 status

Action:

Algae-oil supplement: 250–500 mg combined EPA+DHA daily
Background ALA from flaxseed, chia, hemp, walnuts
Pregnancy/lactation: 200–300 mg DHA daily
See vegan omega-3 ALA vs algae

Threshold for testing: Generally not routine. Consider during pregnancy planning.

6. Iodine

Risk level: Moderate. Plant foods are generally low in iodine; seaweed is variable. Iodine deficiency during pregnancy is particularly concerning.

Function: Thyroid hormone synthesis (T3, T4); metabolic regulation; foetal development.

Signs of deficiency:

Goitre (visible thyroid enlargement)
Hypothyroidism symptoms (fatigue, cold intolerance, weight gain, hair loss)
Pregnancy: foetal cretinism, intellectual disability

Tests:

Urine iodine concentration (not routine)
Serum TSH (thyroid-stimulating hormone) — primary clinical thyroid marker
Free T4

Action:

Iodised salt regularly (¼ tsp = ~76 mcg)
150 mcg potassium iodide supplement if not using iodised salt
Pregnancy: 220 mcg/day (typically in prenatal vitamin); verify
Avoid: high-dose seaweed (kelp tablets) — can contain excessive iodine

Threshold for testing: Pregnancy planning; persistent thyroid symptoms.

7. Zinc

Risk level: Lower. Phytates reduce absorption modestly, but a varied vegan diet typically meets needs.

Function: Immune function, wound healing, taste perception, DNA synthesis.

Signs of deficiency:

Frequent illness
Slow wound healing
Hair loss
Loss of taste / smell
Skin issues (eczema, acne flare)
Diarrhoea (severe deficiency)

Tests:

Serum zinc (limited; can fluctuate)
Hair or red blood cell zinc (less common)

Action:

Pumpkin seeds (1 oz = 2.2 mg)
Hemp seeds, cashews, tahini
Legumes, tofu, oats, quinoa
Vegan multivitamin includes 8–15 mg
Standalone zinc supplement (15–30 mg) for documented deficiency or short-term illness recovery

Threshold for testing: Symptomatic individuals.

8. Choline

Risk level: Lower but often-overlooked. Plant choline content is moderate; pregnancy and lactation needs are higher.

Function: Neurotransmitter synthesis (acetylcholine), liver function, foetal neural development.

Signs of deficiency:

Fatty liver (extreme cases)
Fatigue
Cognitive issues
Pregnancy: under-supply may affect fetal neural development

Tests:

Not routinely tested

Action:

Soybeans, tofu, tempeh
Quinoa, wheat germ, peanuts
Brussels sprouts, broccoli, cauliflower
Aim for 425–550 mg/day
Supplement if pregnant (200–400 mg choline bitartrate or sunflower lecithin)

Threshold for testing: Pregnancy planning.

Other potential considerations

Selenium: Largely covered by 1–3 Brazil nuts daily. Soil variability means selenium-poor regions may warrant attention.
Magnesium: Whole-food vegan diets typically high; deficiency rare.
Vitamin K2: Limited plant sources (natto). Some experts recommend supplementation; evidence base less robust than for K1.
Creatine: Lower baseline in vegans; relevant for athletes (3–5g/day supplementation common).
Taurine, carnosine, carnitine: Body synthesises adequately for most adults. Athletic populations sometimes supplement; evidence is mixed.
Vitamin A: Vegan diet relies on beta-carotene conversion. Genetic polymorphisms affect conversion efficiency in ~30% of population. Deficiency rare in well-fed populations; persistent night-vision issues warrant testing.

A reasonable annual baseline

For an adult who’s been vegan 12+ months, a reasonable annual or biannual blood test panel:

B12 (with MMA if low-normal)
Ferritin
Vitamin D 25(OH)D
Thyroid: TSH (and free T4 if abnormal)
Standard CBC and lipid panel (general health)

For pregnant or planning-pregnancy: add the standard antenatal panel plus folate, iodine, choline awareness.

For athletes: add ferritin checks twice yearly.

When to consult a registered dietitian

First vegan pregnancy
First vegan child
Persistent fatigue not explained by sleep
Documented deficiency (low ferritin, low B12, low vitamin D)
Athletic populations with high training loads
Eating disorder history
Pre-existing condition (diabetes, kidney disease, autoimmune)

The Vegan RD network and the Academy of Nutrition and Dietetics’ Vegetarian Nutrition Dietetic Practice Group help locate specialists.

Bottom line

Eight nutrients warrant attention on a vegan diet — B12 most strictly, vitamin D and iron commonly, calcium and omega-3 with planning, iodine and zinc with awareness, choline particularly for pregnancy. Each has a known answer. Testing 6–12 months into transition and annually thereafter (or as symptoms warrant) catches issues early. None of these are barriers; all are planning items.

Always discuss specific deficiencies with a healthcare provider.