How to Know If You’re Deficient in Iron, Vitamin D, or B12

Feeling constantly tired, low on energy, or unusually moody? You might not just be stressed — your body could be running low on essential nutrients. Iron, Vitamin D, and Vitamin B12 deficiencies are especially common in women and often go undiagnosed. In this article, we’ll break down the signs, symptoms, causes, and tests for each deficiency so you can better understand what your body is trying to tell you.

Why These 3 Nutrients Matter So Much

1. Iron

Iron helps your red blood cells carry oxygen throughout your body. Without enough iron, your body struggles to fuel your organs, leading to fatigue and weakness.

2. Vitamin D

Vitamin D plays a major role in bone health, immune support, and even mood regulation. Since it comes mainly from sunlight, many women don’t get enough — especially if they live in colder climates or wear sunscreen regularly.

3. Vitamin B12

B12 keeps your brain sharp and supports your nervous system. It also helps make DNA and red blood cells. Vegetarian or vegan? You’re at a higher risk of B12 deficiency since it’s mostly found in animal products.

Common Signs You’re Deficient

Iron Deficiency Symptoms:

Fatigue or exhaustion
Pale skin and dark circles
Brittle nails or hair loss
Shortness of breath
Restless leg syndrome
Frequent headaches

Pro tip: If your periods are heavy, you’re more likely to lose iron monthly and may need supplements.

Vitamin D Deficiency Symptoms:

Bone pain or muscle weakness
Mood swings or depression
Frequent colds or flu
Hair thinning
Low energy despite rest

Note: Women with darker skin produce less vitamin D from sunlight and may require higher supplementation.

B12 Deficiency Symptoms:

Brain fog or memory issues
Tingling or numbness in hands/feet
Balance problems or dizziness
Swollen or sore tongue
Low mood or irritability

Real talk: B12 deficiency can mimic mental health issues like anxiety or depression.

Causes of Nutrient Deficiency in Women

Poor diet (low in iron-rich or fortified foods)
Heavy menstrual bleeding (iron loss)
Lack of sun exposure (vitamin D)
Vegan or vegetarian diets (B12)
Digestive disorders like IBS, celiac, or Crohn’s
Pregnancy or breastfeeding (higher nutrient demand)

How to Get Tested (It’s Easier Than You Think)

1. Iron Testing

Ferritin test – checks stored iron
Hemoglobin levels – checks for anemia
Ask your doctor for a CBC (complete blood count) and ferritin test.

2. Vitamin D Testing

25-hydroxy vitamin D blood test – most accurate
Ranges:
Deficient: < 20 ng/mL
Insufficient: 20–30 ng/mL
Optimal: 30–50 ng/mL

3. B12 Testing

Serum B12 blood test
MMA (methylmalonic acid) – may be more accurate
Low B12 can show up as low-normal in blood, so additional testing may be needed.

What to Do If You’re Deficient

Iron:

Food sources: red meat, spinach, lentils, tofu, fortified cereals
Tips: Pair iron with Vitamin C (like oranges or tomatoes) to boost absorption
Supplements: ferrous sulfate or ferrous gluconate (check with your doctor)
Warning: Too much iron can be toxic — don’t self-medicate.

Vitamin D:

Sunshine: 15–30 minutes on bare skin (arms/legs) a few times a week
Food sources: fatty fish, egg yolks, fortified milk or orange juice
Supplements: D3 is more effective than D2
Dosage: Most adults need 1000–2000 IU daily — some may need more under doctor supervision

Vitamin B12:

Food sources: eggs, dairy, poultry, fish, fortified plant milk
Vegans: must supplement — oral B12 or injections
Supplements: cyanocobalamin or methylcobalamin forms
Note: B12 is water-soluble — excess is usually flushed out, but follow dosage guidelines

Natural Lifestyle Tweaks That Help

Add leafy greens, beans, and fortified cereals to your weekly meals
Take a walk in the sun daily (without sunscreen for 15 minutes)
Plan balanced meals with protein, fiber, and healthy fats
Use a multivitamin or targeted supplements if recommended
Keep track of mood, energy, and cycles — these are often nutrient-linked

When to See a Doctor

Get tested if:

You feel unusually tired for weeks
Your period is heavy and you feel drained afterward
You follow a vegan/vegetarian diet
You’ve recently had a baby
You live in low-sunlight areas

Early detection = easier recovery.

Final Thoughts: Listen to Your Body

Your body gives you signals when something’s off. Nutrient deficiencies are common, but they’re also manageable with awareness, testing, and simple lifestyle changes. Don’t wait for symptoms to worsen. If you suspect low iron, vitamin D, or B12, talk to your healthcare provider and take action.