Top 10 Most Common Vitamin Deficiencies Worldwide

Hook Introduction

More than 2 billion people worldwide are living with common vitamin deficiencies and vitamin and mineral deficiencies they may not even know about, according to World Health Organization estimates.

Some of these gaps cause vague fatigue that gets brushed off for years. Others cause preventable blindness in children. We reviewed WHO, Global Burden of Disease, and peer-reviewed 2025–2026 data to rank the deficiencies affecting the most people worldwide, and what actually drives them.

Key Highlights (Quick Facts)

• The World Health Organization estimates over 2 billion people globally suffer from some form of vitamin or mineral deficiency.
• Iron deficiency is the single most common micronutrient deficiency worldwide, affecting more than one-third of the global population, according to Global Burden of Disease data.
• WHO reported that more than 40% of children and pregnant women globally suffered from anemia in its most recent global estimate, a large share driven by iron deficiency.
• Vitamin D deficiency affects an estimated nearly 1 billion people globally, with prevalence varying sharply by latitude, season, and skin-sun exposure patterns.
• Vitamin A deficiency affects an estimated 190 million preschool-age children worldwide and remains the leading cause of preventable childhood blindness.
• Iodine and vitamin A deficiency incidence in children fell by 92.9% and 94.9% respectively between 1990 and 2021, while dietary iron deficiency has stagnated, particularly in conflict-affected regions, per a 2025 Global Burden of Disease analysis.
• Low socio-demographic-index regions show 7.3 times higher iodine deficiency and 151 times higher vitamin A deficiency disability-adjusted life year (DALY) rates than high-income regions.
• In the US, CDC nutrition monitoring found the prevalence of folate insufficiency and iron deficiency rose nearly 6 percentage points in women of reproductive age in its most recent reporting period.

A Note Before You Read Further

This article is for general educational purposes and is not a substitute for medical advice or diagnosis. Deficiency prevalence varies enormously by country, age group, diet, and individual health status — a global statistic doesn’t tell you anything about your own levels.

The only reliable way to know if you have a vitamin or mineral deficiency is a blood test ordered by a healthcare provider. Please don’t start high-dose supplementation based on symptoms alone, especially for fat-soluble vitamins like A and D, which can reach toxic levels with excessive, unsupervised use. If you suspect a deficiency, especially during pregnancy or in a child, talk to a doctor first.

How We Ranked These Deficiencies

We weighed four things: global prevalence (population affected), disease burden as measured by disability-adjusted life years (DALYs) in Global Burden of Disease data, health severity of untreated deficiency, and how unevenly the deficiency is distributed across income levels and regions — since several of these gaps are heavily concentrated in specific vulnerable populations rather than spread evenly worldwide.

The Top 10 Most Common Vitamin and Mineral Deficiencies

1. Iron Deficiency

Iron deficiency is the most common micronutrient deficiency on Earth, affecting more than one-third of the global population, according to Global Burden of Disease trend data. It’s the leading cause of microcytic anemia, producing fatigue, weakness, shortness of breath, and dizziness that many people live with for years without connecting it to their diet.

The burden falls heaviest on children and pregnant women: WHO’s global estimate found more than 40% of children and pregnant women worldwide suffered from anemia, a large share attributable to iron deficiency specifically. Unlike iodine and vitamin A deficiency, which have declined sharply since 1990, dietary iron deficiency has stagnated globally, and 41.7% of children under five worldwide remain iron deficient, according to a 2025 Global Burden of Disease analysis in children — with conflict-affected regions showing the least improvement.

Who’s most at risk: Menstruating women, pregnant women, young children, people with plant-based diets low in bioavailable iron, and anyone with chronic blood loss.

2. Vitamin D Deficiency

Vitamin D deficiency affects an estimated nearly 1 billion people globally, according to a large pooled analysis of 7.9 million participants published in Frontiers in Nutrition. Because vitamin D is synthesized primarily through skin exposure to sunlight, prevalence varies dramatically by latitude, season, skin pigmentation, and time spent outdoors — making it one of the most geographically uneven deficiencies on this list.

Interestingly, US CDC nutrition monitoring shows a more complex national picture: mean serum vitamin D concentrations have actually increased roughly 20% since the early 2000s, likely reflecting increased supplementation and fortification, even as deficiency remains common in specific groups, including older adults, people with limited sun exposure, and those with darker skin living at higher latitudes.

Who’s most at risk: People with limited sun exposure, older adults, people with darker skin pigmentation living far from the equator, and people who are obese (vitamin D is fat-soluble and can be sequestered in fat tissue).

3. Vitamin B12 Deficiency

Vitamin B12 deficiency prevalence varies enormously depending on the population studied — a 2025 Saudi Arabian national survey found a laboratory-confirmed prevalence of 5.5% in the general adult population, while a study of type 2 diabetes patients on long-term metformin therapy found a prevalence of 36.5%, illustrating how much specific medical conditions and medications can elevate individual risk far above general population rates.

B12 is found almost exclusively in animal products, making strict vegans and vegetarians a particularly high-risk group without supplementation or fortified foods. Long-term metformin use, a first-line diabetes medication taken by hundreds of millions of people worldwide, is a well-documented risk factor for reduced B12 absorption over time.

Who’s most at risk: Vegans and vegetarians without supplementation, older adults with reduced stomach acid, people on long-term metformin therapy, and people who’ve had certain gastric or bariatric surgeries.

4. Vitamin A Deficiency

Vitamin A deficiency remains the leading cause of preventable childhood blindness worldwide, affecting an estimated 190 million preschool-age children globally. WHO has previously estimated that more than 250 million children develop some degree of blindness due to vitamin A deficiency, and roughly half of those children die within a year of losing their sight — underscoring how severe untreated deficiency can become in vulnerable populations.

The encouraging news: vitamin A deficiency incidence in children fell by nearly 95% between 1990 and 2021, one of the strongest public health improvements of any deficiency on this list, largely credited to targeted supplementation and food fortification programs. But the burden remains sharply unequal — low-income regions show DALY rates 151 times higher than high-income regions, meaning the remaining burden is now heavily concentrated rather than globally distributed.

Who’s most at risk: Children in low- and middle-income countries, particularly in regions with limited access to fortified foods or supplementation programs; people with fat-malabsorption conditions.

5. Iodine Deficiency

Iodine deficiency is a leading cause of preventable brain damage in childhood, and historically caused visible goitre and, in severe cases, intellectual disability. Like vitamin A deficiency, it has seen a dramatic global decline — incidence fell 92.9% between 1990 and 2021, with associated disease burden (DALYs) dropping nearly 99% over the same period, driven largely by widespread salt iodization programs.

Despite this progress, iodine deficiency hasn’t disappeared, and low-income regions still show iodine deficiency DALY rates 7.3 times higher than high-income regions. Notably, iodine deficiency has also re-emerged as a concern in some higher-income countries in recent decades, as dietary patterns shift away from iodized salt toward processed foods and specialty diets that don’t reliably include it.

Who’s most at risk: People in regions without salt iodization programs, pregnant women (iodine needs increase significantly during pregnancy), and people following restrictive diets that exclude iodized salt or seafood.

6. Folate (Vitamin B9) Deficiency

Folate deficiency has drawn renewed attention from US public health monitoring. CDC’s long-term nutrition surveillance found that mean serum and red blood cell folate concentrations decreased 10–30% since the early 2000s, and the prevalence of folate insufficiency increased nearly 6 percentage points in women of reproductive age in the most recent monitoring period — a concerning trend given folate’s critical role in preventing neural tube defects during early pregnancy.

Folate deficiency often travels alongside iron deficiency in the same at-risk populations, and both are frequently addressed together through prenatal supplementation programs, since both nutrients are critical during the first weeks of pregnancy, often before a person knows they’re pregnant.

Who’s most at risk: Women of reproductive age (especially those not taking prenatal vitamins or folic acid supplements), people with certain malabsorption conditions, and heavy alcohol users.

7. Zinc Deficiency

Zinc deficiency is consistently grouped among the most common global micronutrient deficiencies alongside iron, vitamin A, iodine, and folate in Global Burden of Disease tracking. It contributes to impaired immune function, growth delays in children, and slower wound healing, and disproportionately affects populations with diets low in animal protein and high in phytate-rich grains and legumes that inhibit zinc absorption.

Because zinc deficiency symptoms overlap significantly with other nutritional gaps — fatigue, reduced immune resilience, slow healing — it’s frequently under-recognized and under-tested compared to more commonly screened nutrients like iron and vitamin D.

Who’s most at risk: People with primarily plant-based, grain-heavy diets in low-income regions, people with chronic diarrheal disease, and pregnant or breastfeeding women with elevated needs.

8. Vitamin B6 Deficiency

Vitamin B6 deficiency is less frequently highlighted in global prevalence statistics than iron or vitamin D, but it remains clinically significant, particularly among older adults, people with kidney disease, and those on certain long-term medications (including some anti-seizure and tuberculosis drugs) that interfere with B6 metabolism.

It plays a central role in amino acid metabolism and neurotransmitter synthesis, and untreated deficiency has been linked to anemia, skin changes, and neurological symptoms — though isolated B6 deficiency is less common globally than the deficiencies ranked above it, often appearing alongside other B-vitamin gaps rather than in isolation.

Who’s most at risk: Older adults, people with chronic kidney disease, people on long-term isoniazid or certain anti-seizure medications, and heavy alcohol users.

9. Vitamin C Deficiency

Severe vitamin C deficiency (scurvy) is now uncommon in wealthy nations, but mild-to-moderate insufficiency remains more common than most people assume, particularly among smokers (who require higher intake due to increased oxidative stress), people with very restricted diets, and older adults in institutional care settings with limited access to fresh produce.

Because vitamin C requirements increase with smoking and certain chronic conditions, and because it’s water-soluble and not stored long-term in the body, insufficiency can develop relatively quickly in people who go through periods of very limited fruit and vegetable intake.

Who’s most at risk: Smokers, people with very limited fresh fruit and vegetable access, older adults in care facilities, and people with malabsorption conditions.

10. Calcium Deficiency

Calcium deficiency frequently travels alongside vitamin D deficiency, since vitamin D is required for effective calcium absorption in the gut — meaning the two often need to be addressed together rather than in isolation. Chronic low calcium intake is strongly linked to reduced bone density and elevated osteoporosis risk over time, particularly in postmenopausal women.

Dairy avoidance (whether due to lactose intolerance, allergy, or dietary choice), limited access to fortified plant-based alternatives, and inadequate vitamin D status are the most common overlapping drivers, making calcium deficiency a useful reminder that many nutrient gaps compound each other rather than occurring in isolation.

Who’s most at risk: Postmenopausal women, people with lactose intolerance or dairy allergies avoiding fortified alternatives, and people with coexisting vitamin D deficiency.

Important Statistics Table

Deficiency	Global Prevalence / Scale	Most Affected Group	Trend (1990–2021)
Iron	33%+ of global population; 41.7% of under-5s	Menstruating/pregnant women, young children	Stagnant, worsening in conflict zones
Vitamin D	~1 billion people	Limited sun exposure, older adults	Mixed — improving in some high-income countries
Vitamin B12	5.5%–36.5% depending on population/risk group	Vegans, older adults, metformin users	Limited global trend data
Vitamin A	190 million preschool children	Children in low-income regions	Declined ~95%
Iodine	7.3x higher DALY burden in low-income regions	Regions without salt iodization	Declined ~93%
Folate	Rising in specific groups (US data)	Women of reproductive age	Worsening in monitored US population
Zinc	Grouped among top 5 global deficiencies	Plant-based, grain-heavy diets	Under-tracked globally
Vitamin B6	Less quantified globally	Older adults, certain medications	Under-tracked globally
Vitamin C	Uncommon severe form; mild insufficiency more common	Smokers, limited produce access	Largely stable in wealthy nations
Calcium	Frequently coexists with vitamin D deficiency	Postmenopausal women, dairy avoidance	Compounds with vitamin D trends

Sources: WHO Vitamin and Mineral Nutrition Information System, Global Burden of Disease 2019/2021 studies, CDC Nutrition Report, Frontiers in Nutrition pooled analysis, PMC 2025 studies. Prevalence estimates vary by methodology, population studied, and testing threshold used — treat as directional rather than exact for any individual.

Step-by-Step: What to Do If You Suspect a Deficiency

1. Don’t self-diagnose from symptoms alone. Fatigue, brain fog, and low mood overlap across many deficiencies (and many non-deficiency conditions) — symptoms alone can’t tell you which nutrient, if any, is actually low.
2. Ask your doctor for targeted blood testing. Iron studies, vitamin D (25-hydroxyvitamin D), and B12 are the most commonly and reliably tested; ask specifically which panel makes sense for your risk factors.
3. Share your diet and risk factors honestly. Mention if you’re vegan/vegetarian, pregnant, on long-term medications like metformin, or have limited sun exposure — this shapes which deficiencies are actually likely for you.
4. Avoid high-dose self-supplementation before testing, especially for fat-soluble vitamins A and D, which can accumulate to toxic levels with excessive unsupervised use.
5. Retest after starting supplementation. If a deficiency is confirmed and treated, follow-up testing (typically after 8–12 weeks) confirms whether levels are actually improving.
6. Address compounding deficiencies together. If you’re diagnosed with vitamin D deficiency, ask about calcium status too, since the two are functionally linked.

Pros and Cons Table: Testing vs. Supplementing Without Testing

Approach	Pros	Cons
Blood testing before supplementing	Confirms actual deficiency; avoids wasted spending on unneeded supplements; prevents toxicity risk	Requires a doctor’s visit and lab costs; may involve a wait for results
Supplementing based on symptoms alone	Faster, no appointment needed	Risk of masking underlying conditions; risk of toxicity with fat-soluble vitamins; may miss the actual deficiency present
General multivitamin as “insurance”	Low risk at standard doses; may help mild dietary gaps	Doesn’t address a significant, confirmed deficiency at adequate doses; false sense of security

Comparison Table: Deficiency by Risk Group

Risk Group	Deficiencies of Highest Concern	Why
Pregnant women	Iron, folate, iodine	Elevated needs for fetal development; anemia risk in >40% of pregnant women globally
Vegans/vegetarians	Vitamin B12, iron, zinc	These nutrients are far more bioavailable from animal sources
Older adults	Vitamin B12, vitamin D, vitamin B6	Reduced absorption efficiency and stomach acid with age
Children in low-income regions	Vitamin A, iodine, iron	Highest DALY burden concentration globally
People with limited sun exposure	Vitamin D	Primary synthesis route is UVB skin exposure
Smokers	Vitamin C	Increased oxidative stress raises requirement
Postmenopausal women	Calcium, vitamin D	Combined effect accelerates bone density loss
People on long-term metformin	Vitamin B12	Well-documented absorption interference over time

2026 News and Trends

The clearest 2026 story in this space is divergence between success stories and stalled progress. A December 2025 Global Burden of Disease analysis found iodine and vitamin A deficiency in children fell by roughly 93–95% between 1990 and 2021 — a genuine public health triumph driven by fortification programs — while dietary iron deficiency has stagnated globally, with projections indicating continued stagnation, particularly in conflict-affected areas where fortification and healthcare access break down.

US-specific CDC nutrition monitoring published in its ongoing Nutrition Report flags a concerning folate trend: mean serum and red blood cell folate concentrations have declined 10–30% since the early 2000s, alongside a nearly 6 percentage point rise in folate insufficiency among women of reproductive age, a trend worth watching given folate’s critical role in preventing birth defects.

Regional inequality remains the defining pattern across nearly every nutrient tracked. Low socio-demographic-index regions show iodine deficiency burdens 7.3 times higher, and vitamin A deficiency burdens a striking 151 times higher, than high-income regions, meaning global averages mask enormous concentration of remaining risk in specific, identifiable populations rather than even distribution worldwide.

Conclusion

Iron, vitamin D, and vitamin B12 remain the deficiencies affecting the largest number of people worldwide, while vitamin A and iodine deficiency, despite dramatic global progress, still concentrate heavily among children in low-income regions. The pattern across nearly every nutrient on this list is the same: global averages hide enormous inequality in who actually carries the risk.

If you recognize your own risk factors in this list, the right next step is a conversation with a healthcare provider and a blood test, not guessing based on symptoms alone.

References

1. World Health Organization – Vitamin and Mineral Nutrition Information System (VMNIS): https://www.who.int/teams/nutrition-and-food-safety/databases/vitamin-and-mineral-nutrition-information-system
2. CDC – About CDC’s Nutrition Report: https://www.cdc.gov/nutrition-report/about/index.html
3. Frontiers in Nutrition – Global and Regional Prevalence of Vitamin D Deficiency in Population-Based Studies from 2000 to 2022 (pooled analysis of 7.9 million participants): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10064807/
4. PubMed/Frontiers in Nutrition – Epidemiological Trends and Disparities in Iodine, Vitamin A, and Iron Deficiencies Among Children Aged 0-14 Years Globally, 1990-2021: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12728350/
5. ScienceDirect – Global, Regional, and National Burdens of Common Micronutrient Deficiencies from 1990 to 2019 (GBD 2019 analysis): https://www.sciencedirect.com/science/article/pii/S2589537022000293
6. PMC – Global, Regional and National Trends in the Burden of Nutritional Deficiencies in Children, 1990-2021: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12263351/
7. PMC – Micronutrient Testing, Supplement Use, and Knowledge Gaps in a National Adult Population: Evidence from Saudi Arabia (2025): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12736049/
8. PMC – Prevalence of Vitamin B12 Deficiency in Patients With Type 2 Diabetes Mellitus on Metformin Therapy: A Cross-Sectional Study: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11498909/
9. iHerb Wellness Hub – The Top 3 Vitamin and Mineral Deficiencies in the World: https://www.iherb.com/blog/top-3-vitamin-and-mineral-deficiencies-worldwide/1634
10. Nature Doctors – Top Nutrient Deficiencies Revealed by Blood Work: What You Need to Know: https://www.thenaturedoctors.ca/blog/top-nutrient-deficiencies-revealed-by-blood-work-what-you-need-to-know

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