When your body runs low on folic acid and B12, you start to feel different. You might feel tired all the time, even after sleeping well. Your hands and feet might tingle like they’re “asleep.” Your tongue could hurt or look different. These are your body’s way of saying, “I need help!”
Both folic acid (also called folate or vitamin B9) and vitamin B12 work together like a team. They help make new red blood cells, keep your nerves healthy, and create DNA. When you don’t have enough of either vitamin, your whole body feels the effects.
In this guide, you’ll learn what symptoms to watch for, who’s most at risk, and when to see a doctor. You’ll also discover how these two vitamins work together and why catching deficiency early matters so much.
How Folic Acid and B12 Work in Your Body
Think of folic acid and B12 as construction workers in your body. They build new cells every single day. Your body needs them to make red blood cells that carry oxygen everywhere. Without enough oxygen, every part of you struggles.
B12 also protects the covering around your nerves. This covering is like insulation on electrical wires. When it breaks down, messages can’t travel properly through your body. That’s when you get tingling, numbness, or worse problems.
Folic acid helps create DNA, which is like an instruction manual for every cell. During pregnancy, babies need lots of folic acid to grow a healthy brain and spine. That’s why pregnant women need extra amounts.
These vitamins also team up to control homocysteine, a substance in your blood. When homocysteine levels get too high, it increases your risk of heart disease. Having enough B12 and folic acid keeps those levels safe.
Common Symptoms That Affect Your Energy
Extreme Tiredness That Won’t Go Away
One of the first symptoms of folate deficiency is extreme tiredness (fatigue). This isn’t normal “end of the day” tired. It’s a deep exhaustion that makes you want to sleep all the time.
You might feel tired because your red blood cells aren’t working right. When you lack vitamin B12 or folate, your body makes abnormally large red blood cells that cannot function properly. These oversized cells can’t carry oxygen well. Without enough oxygen, every task feels harder.
Even simple things like climbing stairs or carrying groceries can wear you out. You might need to rest more often or take naps during the day. This fatigue usually gets worse over weeks or months.
Feeling Weak and Low on Strength
Muscle weakness often comes with the tiredness. Your muscles need oxygen to work properly. When your blood can’t deliver enough oxygen, you feel weak and shaky.
You might notice:
- Trouble lifting things you used to lift easily
- Your legs feel heavy when walking
- Needing to sit down more often
- Getting out of breath during normal activities
Shortness of breath and feeling dizzy are common symptoms. Your heart might beat faster than normal, trying to pump more blood to make up for the lack of oxygen.
Pale or Yellow Skin
Your skin might look paler than usual. Some people even develop a slightly yellow tint called jaundice. This happens because the weak red blood cells break down faster than normal.
When red blood cells break down, they release a substance called bilirubin. Too much bilirubin gives your skin and the whites of your eyes a yellowish color.
Symptoms That Affect Your Brain and Nerves
Tingling and Numbness
Vitamin B12 deficiency can cause symptoms that affect your brain and nervous system (neurological symptoms), including pins and needles sensations. Many people describe it as feeling like their hands or feet “fell asleep” but the feeling never goes away.
This tingling usually starts in your hands and feet. It might spread up your arms and legs over time. The medical name for this is paresthesia.
Neurological symptoms, such as paresthesias, ataxia, and loss of proprioception, are typically seen in vitamin B12 deficiency but are generally absent in isolated folate deficiency. This helps doctors figure out which vitamin you’re missing.
Balance and Walking Problems
B12 deficiency can affect how you walk and keep your balance. You might feel unsteady on your feet or bump into things more often.
Some people develop ataxia, which means trouble coordinating movements. You might notice:
- Stumbling or tripping more
- Difficulty walking in a straight line
- Needing to hold onto walls or furniture
- Trouble with fine motor skills like buttoning shirts
These problems happen because B12 protects the nerves that control movement. When those nerves get damaged, your body can’t coordinate movements as well.
Memory and Thinking Issues
Vitamin B12 deficiency can cause problems with thinking, which doctors refer to as cognitive impairment. These issues include difficulty thinking or reasoning and memory loss.
You might notice:
- Forgetting things you just learned
- Trouble focusing on tasks
- Taking longer to make decisions
- Feeling confused or “foggy”
- Difficulty finding the right words
Some evidence suggests a link between low vitamin B12 levels to a higher risk of dementia, Alzheimer’s disease, and Parkinson’s disease. That’s why catching deficiency early is so important.
Mood Changes and Depression
Both vitamins affect chemicals in your brain that control mood. Folate deficiency may specifically affect central monoamine metabolism and aggravate depressive disorders.
You might feel:
- Sad or depressed for no clear reason
- More irritable than usual
- Anxious or worried
- Less interested in things you normally enjoy
Depression, irritability, and mood changes are symptoms of folate deficiency, especially in older adults.
Symptoms That Affect Your Mouth and Tongue
Sore, Red, Swollen Tongue
Glossitis refers to a smooth, red, and painful (“beefy”) tongue, often accompanied by oral ulcers. Your tongue might look shiny and feel very sore.
The surface of your tongue can change texture. Instead of the normal bumpy surface, it becomes smooth. The color turns bright red or even slightly purple. Eating spicy or hot foods hurts even more.
A tender, red tongue, mouth sores or mouth ulcers, and reduced sense of taste are symptoms of folate deficiency. These mouth problems can make eating difficult and take away the pleasure of meals.
Mouth Sores and Ulcers
Small, painful sores might appear inside your mouth. These ulcers can show up on your gums, inside your cheeks, or under your tongue. They make talking and eating uncomfortable.
Trouble Tasting Food
Vitamin B12 deficiency can lead to taste disorders, characterized by decreased taste sensitivity, tongue pain, and abnormal tongue sensations. Food might seem bland or taste different than it used to.
This can lead to poor appetite and weight loss. When food doesn’t taste good, you don’t feel like eating. Over time, this makes the deficiency even worse.
Other Physical Symptoms to Watch For
Fast or Irregular Heartbeat
A fast heart rate may be a symptom of vitamin B12 deficiency. The heart may start to beat faster to make up for the reduced number of red blood cells in the body.
You might notice your heart racing or pounding, even when you’re resting. This is your heart working overtime to deliver oxygen throughout your body.
Vision Changes
Some people develop blurred or disturbed vision. This happens when nerve damage affects the optic nerve that connects your eyes to your brain. The medical term is optic neuropathy.
Vision problems from B12 deficiency are serious. They need quick treatment to prevent permanent damage.
Headaches and Dizziness
Feeling dizzy is a common symptom of vitamin deficiency anemia. You might feel lightheaded when you stand up or move around.
Headaches can happen because your brain isn’t getting enough oxygen. These headaches might be dull and constant or come and go.
Cold Hands and Feet
Your hands and feet might feel cold all the time, even in warm weather. This happens because blood isn’t circulating well to your extremities.
The Big Difference Between B12 and Folate Deficiency Symptoms
Most symptoms look the same whether you’re low on B12 or folic acid. Both cause tiredness, weakness, and anemia. But there’s one big difference that helps doctors figure out which vitamin you need.
Neurological symptoms are typically absent in folate deficiency (unlike vitamin B12 deficiency). The tingling, numbness, balance problems, and nerve damage usually only happen with B12 deficiency.
If you have anemia symptoms plus nerve problems, you probably need B12. If you only have anemia symptoms without nerve issues, it might be folic acid deficiency.
However, having normal folate levels doesn’t mean your B12 is fine. You can be low on both at the same time. That’s why doctors test for both vitamins together.
Who Is Most at Risk for Deficiency
People Who Follow Plant-Based Diets
Vitamin B12 isn’t found in plants. B12 is mainly found in meat, eggs and dairy products. Vegetarians and vegans are at a high risk of B12 deficiency.
If you’re vegan or vegetarian, you need to:
- Eat foods with added B12 (fortified cereals, plant milk)
- Take a B12 supplement
- Get B12 injections if your levels are very low
Although it has long been known that strict vegetarians (vegans) are at risk for vitamin B12 deficiency, evidence now indicates that low intakes of animal-source foods, such as occur in some lacto-ovo vegetarians, can also cause vitamin B12 depletion.
The good news? Data from the EPIC-Oxford study showed that vegan participants had the highest levels of folate in their blood. So if you eat lots of leafy greens and beans, your folic acid is probably fine. But you still need to watch your B12.
Older Adults
The prevalence of vitamin B12 deficiency is approximately 6% in persons younger than 60 years, and nearly 20% in those older than 60 years. As you age, your stomach makes less acid. You need stomach acid to absorb B12 from food.
Both vitamin B12 deficiency and folate deficiency are more common in older people, affecting around 1 in 10 people aged 75 or over and 1 in 20 people aged 65 to 74.
Many older adults also take medications that make absorption harder. Antacids and diabetes drugs can block B12 absorption over time.
Pregnant Women
During pregnancy, your body needs much more folic acid. Folate is especially important during pregnancy, as it aids in fetal development.
Folate deficiency during pregnancy can cause severe birth defects called neural tube defects, including spina bifida and anencephaly. It can also cause placental problems and premature birth.
That’s why doctors tell all women who might get pregnant to take 400 micrograms of folic acid every day. If you have diabetes or had a baby with a birth defect before, you need even more – 4 to 5 milligrams daily.
People With Digestive Problems
Certain stomach and intestine problems make it hard to absorb these vitamins:
- Crohn’s disease
- Celiac disease
- Gastric bypass surgery
- Removal of part of the stomach or intestines
Intestinal conditions like Crohn’s disease and celiac disease can keep the body from taking in vitamin B12. If you have any of these conditions, your doctor should check your vitamin levels regularly.
People Taking Certain Medications
Some medicines block vitamin absorption:
- Metformin (diabetes medicine)
- Proton pump inhibitors (PPIs for heartburn)
- H2 blockers (antacids)
- Some seizure medications
Certain medicines, including anticonvulsants and proton pump inhibitors (PPIs), can affect how much of these vitamins your body absorbs. If you take these medicines long-term, ask your doctor about testing your vitamin levels.
People Who Drink Too Much Alcohol
Alcohol abuse causes the liver to run out of stored nutrients, causing the body to draw nutrients out of the bloodstream. This can cause deficiencies of Vitamin A, calcium, Vitamin B12 and Vitamin B9.
Heavy drinking damages your stomach, liver, and intestines. All these organs play a role in absorbing and storing vitamins. Alcohol also destroys B vitamins directly in your digestive system.
How Deficiency Gets Diagnosed
If you have symptoms, your doctor will start with a blood test. Vitamin B12 or folate deficiency can often be diagnosed based on your symptoms and the results of a blood test.
The tests check:
- Your red blood cell count and size
- How much hemoglobin you have (the oxygen-carrying protein)
- Your B12 blood level
- Your folate blood level
A blood level of vitamin B12 less than 148-185 pmol/L (200 to 250 pg/mL) in adults indicates deficiency.
Sometimes the tests need to go deeper. If your B12 level is borderline, your doctor might test for:
- Methylmalonic acid (MMA) – gets high when B12 is low
- Homocysteine – gets high when either vitamin is low
These tests are more sensitive. They can catch deficiency before it causes major problems.
Why Early Treatment Matters So Much
It’s important for vitamin B12 or folate deficiency anaemia to be diagnosed and treated as soon as possible. This is because although many of the symptoms improve with treatment, some problems caused by the condition can be irreversible.
The nerve damage from B12 deficiency can become permanent if you wait too long. Even with treatment, some people never fully recover their nerve function.
That’s why you shouldn’t ignore symptoms like:
- Tingling that lasts more than a few days
- Balance problems
- Memory issues that get worse
- Extreme fatigue that doesn’t improve with rest
Early treatment can reverse most symptoms within weeks or months. But the longer you wait, the harder it gets to fix the damage.
Treatment Options That Work
For B12 Deficiency
Vitamin B12 supplements are usually given by injection at first. Then, depending on whether your B12 deficiency is related to your diet, you’ll either require B12 tablets between meals or regular injections.
If you can absorb B12, oral supplements work well. Methylated B12 supplements are often better than regular B12 because they’re already in the active form your body uses.
For people who can’t absorb B12 well, injections are needed. These shots bypass your digestive system and put B12 directly into your bloodstream.
Learn more about why methylated B12 is recommended for certain conditions and how to take methylated B12 for maximum absorption.
For Folic Acid Deficiency
Folic acid tablets are used to restore folate levels. These usually need to be taken for four months. Most people take 1 to 5 milligrams daily.
Pregnant women need higher doses – usually 400 to 800 micrograms daily, and sometimes more if they’re at high risk.
You can also increase folate through food by eating:
- Leafy green vegetables (spinach, kale, lettuce)
- Broccoli and Brussels sprouts
- Peas and beans
- Citrus fruits
- Fortified breakfast cereals
Important Warning About Treatment
Before you start taking folic acid, your GP will check your vitamin B12 levels to make sure they’re normal. This is because folic acid treatment can sometimes improve your symptoms so much that it masks an underlying vitamin B12 deficiency.
If you take folic acid when you really need B12, the folic acid can hide the anemia symptoms. Meanwhile, the B12 deficiency keeps damaging your nerves. By alleviating the anemia, folic acid supplements were said to “mask” the underlying vitamin B12 deficiency, thus allowing neurological damage to continue or possibly be exacerbated.
That’s why doctors always check both vitamins before starting treatment.
How Fast You’ll Feel Better
Reticulocytosis typically occurs by days 3 to 4; anemia begins to improve within 1 to 2 weeks and usually resolves within 4 to 8 weeks.
Most people notice their energy coming back first. Within days or a few weeks, you’ll feel less tired. Your mood might improve too.
The nerve symptoms take longer to heal. Tingling and numbness might take months to go away completely. Balance problems can take even longer.
Some people need to take supplements for the rest of their lives, especially if:
- They can’t absorb vitamins well
- They had stomach surgery
- They have pernicious anemia
- They follow a strict vegan diet
Regular follow-up with your doctor helps make sure your treatment is working.
Preventing Deficiency Before It Starts
Eat a Balanced Diet
The best prevention is eating foods rich in both vitamins. For B12, eat:
- Meat, poultry, and fish
- Eggs and dairy products
- Fortified cereals and plant milks (for vegans)
For folate, eat:
- Dark leafy greens
- Beans, lentils, and peas
- Oranges and other citrus fruits
- Avocados
- Asparagus
Take Supplements When Needed
If you’re at risk, don’t wait for symptoms. Consider a methylated B12 supplement that includes both methylcobalamin and methylfolate.
Methylated forms are especially helpful for people with MTHFR gene variations who can’t process regular B12 and folic acid well.
Check out the benefits of methylated B12 to see if supplementation makes sense for you.
Get Regular Checkups
If you’re in a high-risk group, ask your doctor to check your vitamin levels every year. This is especially important if you:
- Are over age 60
- Follow a plant-based diet
- Take medications that affect absorption
- Have digestive problems
- Are planning to get pregnant
Catching low levels early means you can fix them before symptoms start.
Special Considerations for Different Groups
For Seniors
Vegetarians, vegans and elderly people are at higher risk for B12 deficiency. If you’re over 60, talk to your doctor about B12 supplementation even if you eat meat.
Many older adults need regular B12 injections or high-dose supplements. Your stomach acid decreases with age, making it harder to absorb B12 from food. Learn more about whether methylated B12 is safe for seniors.
For Vegans and Vegetarians
Long-standing vegans should be monitored for vitamin B12 levels. Don’t assume fortified foods are enough. Most vegans need methylated B12 supplements to maintain healthy levels.
Your folate levels are probably good if you eat lots of plants. But B12 only comes from animal sources or supplements.
For People With MTHFR Gene Variations
MTHFR stands for methylenetetrahydrofolate reductase. Some people have a genetic change (mutation) in their MTHFR gene. If you have this mutation, you aren’t able to convert folate to its active form, 5-MTHF.
This genetic mutation affects about 25% of Hispanic people, 10% of white people, 10% of Asian people and 1% of Black people.
If you have this gene variation, you need supplements that are already methylated. Regular folic acid won’t work as well for you.
Understanding the Relationship Between Both Vitamins
B12 and folic acid work together in something called the “folate trap.” In the setting of vitamin B12 deficiency, folate becomes sequestered in an inactive form.
Think of it like a locked door. Folic acid gets trapped on one side and can’t do its job. B12 is the key that unlocks the door. Without enough B12, you can have plenty of folic acid but still act like you’re deficient.
That’s why treating only one vitamin doesn’t always work. Sometimes you need both to fix the problem.
Serious Complications If Left Untreated
Although it’s uncommon, vitamin B12 or folate deficiency (with or without anaemia) can lead to complications, particularly if you have been deficient in vitamin B12 or folate for some time.
Possible complications include:
- Permanent nerve damage
- Heart problems and heart failure
- Infertility
- Pregnancy complications and birth defects
- Increased stroke risk
- Depression and memory problems
Adults with severe anaemia are at risk of developing heart failure. Your heart works so hard to pump oxygen that it can wear out.
These serious problems don’t happen to everyone. But they show why getting tested and treated matters.
Questions to Ask Your Doctor
When you visit your doctor about possible deficiency, consider asking:
- Should I get tested for both B12 and folate?
- Could my medications be causing low levels?
- Do I need blood tests or other tests?
- Should I take supplements or get injections?
- How long will treatment take?
- Do I need follow-up testing?
- Could I have MTHFR gene variations?
Don’t be afraid to speak up about your symptoms. Doctors can’t help if they don’t know what you’re experiencing.
When to Seek Medical Help Immediately
Most deficiency symptoms develop slowly. But see a doctor right away if you have:
- Sudden vision loss or major vision changes
- Severe confusion or disorientation
- Inability to walk or severe balance problems
- Chest pain or trouble breathing
- Signs of a heart attack
These could mean your deficiency has caused serious complications that need emergency treatment.
Final Thoughts
Folic acid and B12 deficiency can make you feel awful, but the good news is that they’re easy to fix once you know what’s wrong. The symptoms – from tiredness and weakness to tingling hands and mouth sores – are your body’s warning signals.
Don’t ignore these signs. The longer the condition goes untreated, the higher the chance of permanent damage. A simple blood test can tell you if you need more of these vitamins.
Whether you need to change your diet, take supplements, or get injections, treatment works. Most people feel much better within weeks. The key is catching the problem early and sticking with treatment.
If you’re in a high-risk group – older adults, vegans, pregnant women, or people with digestive issues – don’t wait for symptoms. Talk to your doctor about testing your levels now. Prevention is always easier than treatment.
For those who need supplementation, consider methylated B12 products that provide both vitamins in their most absorbable forms. Learn about the difference between methylated B12 and regular B12 to make the best choice for your health.
Your health is worth protecting. If something feels off, trust your instincts and get checked. With proper diagnosis and treatment, you can feel like yourself again.