Signs You Might Have a Vitamin Deficiency (And What to Do About It)

A rundown of common vitamin deficiency symptoms, what causes them, and what to eat (or supplement) to keep your body thriving.

Feeling tired, foggy, or off in ways you can’t quite explain? You might be dealing with a vitamin deficiency.

Danny Roth here, reporting from the NYU Langone waiting room (where I’m due for a lab panel—Celiac kids, you get it). If you’ve landed on this article, chances are you’re interested in nutrition and want to better understand the symptoms of vitamin deficiency before they sneak up on you.

While a balanced diet usually keeps things in check, vitamin deficiencies aren’t uncommon and they’re not always easy to spot. Vitamin deficiencies can affect everything from mood and metabolism to immunity and sleep quality. From restrictive eating to medical conditions, there are several reasons your body might be missing key nutrients. 

Below, we break down the most common vitamins and deficiency symptoms, what causes them, and how to restore balance.

What Causes Vitamin Deficiencies?

There are a few main culprits behind common vitamin deficiencies:

• Restrictive diets, especially those lacking variety

• Digestive conditions (like Celiac disease, Crohn’s, or cystic fibrosis)

• Age and life stage, including pregnancy

• Medications that impact absorption (like PPIs or metformin)

While these signs can stem from many factors, they often point to a lack of vitamins. Symptoms can start subtly—fatigue, brain fog, low immunity—and build over time. And even if you’re taking a multivitamin, deficiency symptoms can still develop if absorption is impaired or if certain nutrients aren’t properly balanced.

As Dr. Kelly Raj noted on the Cleveland Clinic podcast, in the US, these deficiencies are usually “attributable to a certain fad type or a particular diet,” rather than a lack of food access.

1. Vitamin C Deficiency Symptoms

According to registered dietitian Emily Martorano, vitamin C deficiency is surprisingly common, especially among those eating high-protein, low-plant diets.

Common symptoms:

• Fatigue

• Easy bruising

• Bleeding gums

What to eat:

• Citrus fruits, kiwis, pineapple

• Bell peppers, broccoli, Brussels sprouts

Learn more about vitamin C and immunity →

2. Vitamin D Deficiency Symptoms

Dr. Raj cites vitamin D as the most frequently low nutrient in her patients. It’s tricky because symptoms can take time to show up and they can be subtle.

Common symptoms:

• Low energy or fatigue

• Mood changes

• Muscle weakness or bone pain

What to eat:

• Fortified cow’s or soy milk

• Egg yolks, canned tuna, salmon, mushrooms (especially sun-exposed)

Learn more about vitamin D →

3. Vitamin B12 Deficiency Symptoms

Vitamin B12 supports red blood cell production, nerve function, and DNA synthesis. Your body can’t make it. You need to get it from food or supplements.

Common symptoms:

• Fatigue

• Appetite loss or weight loss

• Numbness, tingling, or memory issues (if prolonged)

What to eat:

• Fish (tuna, salmon, sardines)

• Fortified cereals, nutritional yeast

• Eggs, beef, dairy

B12 absorption declines with age, so some people may need regular supplements or injections.

4. Vitamin A Deficiency Symptoms

Vitamin A plays a key role in immune function and eye health. While less common in Western diets, deficiency can still occur—especially in low-fat or highly processed diets.

Common symptoms:

• Dry skin or eyes

• Night blindness

• Increased infections

What to eat:

• Sweet potatoes, carrots, spinach

• Eggs, liver, fortified dairy

Read more about Vitamin A deficiency here

5. Iron Deficiency Symptoms

Iron helps carry oxygen in your blood. Low levels can leave you feeling wiped out.

Common symptoms:

• Tiredness or weakness

• Difficulty concentrating

• Dizziness or lightheadedness

• Cravings for ice or unusual things (like dirt)

What to eat:

• Red meat, shellfish, eggs

• Leafy greens (like spinach or kale)

• Legumes and fortified grains

People who menstruate may need more iron than others. If you’re experiencing recurring fatigue, it’s best to consult your doctor. 

6. Folate (Vitamin B9) Deficiency Symptoms

Folate, also known as vitamin B9, is key for cell growth and DNA production. It’s especially vital during pregnancy to prevent neural tube defects.

Common symptoms:

• Weakness and fatigue

• Anemia

• Irritability or trouble concentrating

What to eat:

• Leafy greens, citrus fruits, beans

• Whole grains, nuts, seafood, and eggs

Folic acid is the supplement version of folate—commonly found in prenatal vitamins.

Read more on why folate matters →

7. Calcium Deficiency Symptoms

We all know calcium is key for strong bones, but it also plays a role in muscle and nerve function.

Common symptoms:

• Numbness or tingling

• Muscle cramps

• Weakened bone density over time

What to eat:

• Dairy products, leafy greens

• Fortified plant milks

• Canned fish with edible bones (like sardines)

Check out our calcium and vitamin D pairing guide →

Bonus: Fiber—The Forgotten Macronutrient

While not a vitamin, fiber is often missing from modern diets. It fuels your gut microbiome and helps keep digestion regular.

Common symptoms of low fiber intake:

• Constipation

• Bloating or irregularity

• Low energy

What to eat:

• Lentils, beans, split peas

• Raspberries, pears, green peas

• Whole grains (like oats, barley, whole-wheat pasta)

Explore our full nutrient list →

Final Thoughts: Don’t Ignore the Symptoms

Your body often knows when something’s off, you just need to learn the language. If you’re noticing signs of vitamin deficiency—like fatigue, mood changes, or recurring illness—your body might be trying to tell you something. If you’ve experienced symptoms of a lack of vitamins, talk to your doctor, get tested, and consider adjusting your diet or supplement routine. The earlier you catch it, the easier it is to fix.

Looking for a simple way to cover your bases? Huel’s products are formulated with all 27 essential vitamins and minerals—convenient, complete, science-backed, and nutrient-rich. 

Words by Danny Roth