ConditionWhole body & general
Nutritional Deficiencies
Nutritional deficiencies occur when the body does not get or absorb enough of a nutrient it needs, such as iron, vitamin D, vitamin B12, folate, iodine, zinc or protein. The most common worldwide is iron deficiency. Causes include a limited diet, increased needs in pregnancy or growth, poor absorption from gut disease or surgery, blood loss, alcohol and some medicines. Symptoms are often vague, such as tiredness, pale skin, hair loss or numbness, so blood tests are key. Most deficiencies are easy to correct.
Also called: Nutrient deficiencies, micronutrient deficiency, vitamin and mineral deficiency, undernutrition
At a glance
- What they are
- Too little of one or more vitamins, minerals or macronutrients for the body's needs.
- Most common
- Iron, vitamin D, vitamin B12, folate, iodine and zinc.
- Causes
- Restrictive diets, increased needs, malabsorption, blood loss, alcohol, medicines, poverty.
- Symptoms
- Fatigue, pale skin, hair loss, brittle nails, mouth sores, numbness, bone pain, poor healing.
- Diagnosis
- Diet history, examination and blood tests.
- Treatment
- Diet changes, supplements and treating the underlying cause.
When to get help
Call 911 or go to the ER
- Confusion, unsteady walking and abnormal eye movements in someone who drinks heavily or is malnourished (possible thiamine deficiency): call 911 or your local emergency number
- Severe breathlessness, chest pain or fainting with severe anemia
See a doctor within a day or two
- Numbness, tingling or weakness in the hands and feet, balance problems, or memory changes (possible B12 deficiency)
- Bleeding gums, easy bruising and poor wound healing with a very limited diet (possible vitamin C deficiency)
- Rapid weight loss, or a child who is not growing or gaining weight
Book a routine appointment
- Persistent tiredness, pale skin or breathlessness on exertion
- Hair loss, brittle or spoon-shaped nails, or cravings for ice or non-food items
- Bone pain or muscle weakness
- Vegan diet, weight-loss surgery, celiac or Crohn's disease, or long-term metformin or acid-reducing medicines
- Planning a pregnancy
Common nutritional deficiencies
| Nutrient | Main roles | Signs of deficiency | Main sources |
|---|---|---|---|
| Iron | Red blood cells, energy | Fatigue, pale skin, breathlessness, hair loss, brittle or spoon nails, craving ice | Red meat, poultry, fish, beans, lentils, fortified cereals |
| Vitamin B12 | Nerves, red blood cells | Fatigue, numbness and tingling, balance problems, sore tongue, memory problems | Meat, fish, eggs, dairy, fortified foods |
| Folate | Cell growth, red blood cells, fetal development | Fatigue, mouth sores, anemia; neural tube defects in pregnancy | Leafy greens, beans, citrus, fortified grains |
| Vitamin D | Bones, muscles, immunity | Bone pain, muscle weakness, falls; rickets in children | Sunlight, oily fish, fortified milk |
| Iodine | Thyroid hormones | Goiter, hypothyroidism; developmental problems in babies | Iodized salt, dairy, seafood |
| Zinc | Immunity, healing, taste | Poor wound healing, hair loss, rashes, loss of taste, diarrhea | Meat, shellfish, nuts, seeds, whole grains |
| Vitamin C | Collagen, immunity | Bleeding gums, bruising, poor healing, corkscrew hairs (scurvy) | Fruits and vegetables |
| Vitamin A | Vision, immunity, skin | Night blindness, dry eyes, infections | Liver, eggs, orange and leafy vegetables |
| Thiamine (B1) | Energy, nerves | Confusion, neuropathy, heart failure | Whole grains, pork, legumes |
| Calcium | Bones, muscles, nerves | Muscle cramps, osteoporosis over time | Dairy, fortified plant milks, leafy greens |
| Protein and calories (malnutrition) | Growth, muscles, immunity | Weight loss, muscle wasting, swelling, poor growth | Varied diet |
Who is at risk
- Pregnant and breastfeeding women: higher needs for iron, folate, iodine and others.
- Infants and young children: rapid growth; iron and vitamin D needs.
- Teenagers, particularly girls with heavy periods.
- Older adults: lower appetite, reduced absorption of B12, less sun exposure.
- Vegans and vegetarians: risk of B12, iron, zinc, iodine, calcium and omega-3 deficiency without planning.
- People with gut conditions: celiac disease, Crohn's disease, chronic pancreatitis, short bowel.
- After weight-loss surgery.
- Heavy alcohol use: thiamine, folate and others.
- People with heavy periods or blood loss.
- Medicines: metformin and acid-reducing medicines (B12), some anti-seizure medicines (folate, vitamin D), diuretics (magnesium, potassium).
- Eating disorders and food insecurity.
- Darker skin, covered clothing or limited time outdoors: vitamin D.
Symptoms
Deficiency symptoms often develop slowly and overlap with many other conditions:
- tiredness and weakness
- pale skin and breathlessness (anemia)
- hair loss and brittle nails
- cracks at the corners of the mouth, a sore or smooth tongue
- numbness, tingling and balance problems
- bone pain and muscle weakness
- frequent infections and slow wound healing
- poor concentration and low mood
- in children: poor growth and development
Diagnosis
A doctor will ask about diet, symptoms, periods, medicines, alcohol and digestive problems, and examine the skin, mouth, nails and nerves. Common blood tests:
- complete blood count
- ferritin and iron studies
- vitamin B12 (and sometimes methylmalonic acid) and folate
- 25-hydroxyvitamin D
- thyroid function, calcium, magnesium, zinc as needed
- tests for underlying causes, such as celiac antibodies or stool tests for blood
Treatment
- Diet changes: a varied diet with vegetables, fruit, whole grains, protein foods and dairy or fortified alternatives. A dietitian can help.
- Supplements: iron, B12 (tablets or injections), folic acid, vitamin D and others, at doses recommended by your doctor or on the label. Taking iron with vitamin C-rich food improves absorption; avoid taking it with tea, coffee or calcium.
- Treat the cause: heavy periods, gut disease, medicines or alcohol use.
- Monitor: repeat blood tests to confirm levels are improving.
Do not take high-dose supplements without advice. Too much iron, vitamin A, vitamin D or other nutrients can be harmful, and iron supplements are a leading cause of poisoning in young children.
Prevention
- Eat a varied diet based on whole foods.
- Take 400 mcg of folic acid daily if you could become pregnant.
- Take vitamin B12 if you follow a vegan diet.
- Consider vitamin D supplements in winter or with limited sun exposure.
- Use iodized salt in moderation.
- Follow lifelong supplement plans after weight-loss surgery.
- Breastfed babies usually need vitamin D drops; ask your pediatrician.
Frequently asked questions
What are the most common nutritional deficiencies?
Worldwide, iron deficiency is the most common, followed by deficiencies of vitamin A, iodine, zinc and folate. In the US and other high-income countries, iron, vitamin D and vitamin B12 deficiencies are the most commonly found.
What are the signs of a vitamin deficiency?
Common signs include fatigue, pale skin, hair loss, brittle nails, mouth sores or cracks, numbness and tingling, bone pain, muscle weakness, frequent infections and poor wound healing. Because these are vague, a blood test is needed to confirm a deficiency.
Can a nutritional deficiency cause hair loss?
Yes. Iron deficiency is a common cause of hair shedding, especially in women. Low zinc, protein, vitamin D and biotin (rare) are also linked to hair loss. Checking ferritin and correcting deficiencies can help hair regrow over several months.
Should I take a multivitamin to prevent deficiencies?
Most healthy people who eat a varied diet do not need a multivitamin. Targeted supplements are recommended for specific groups, such as folic acid before pregnancy, vitamin B12 for vegans, vitamin D for some people, and supplements after weight-loss surgery. Ask your doctor what suits you.
Sources
This guide was written from current patient and clinical guidance, including:
- NIH Office of Dietary Supplements: Dietary supplement fact sheets (iron, vitamin D, vitamin B12, folate, iodine, zinc)
- World Health Organization: Micronutrients
- CDC: Second National Report on Biochemical Indicators of Diet and Nutrition
- MedlinePlus: Malnutrition; Vitamins
- Dietary Guidelines for Americans 2020-2025