You've been on edge for weeks, sleeping badly, tired in a way coffee doesn't touch, and someone suggests it might be your vitamins. So which nutrient deficiencies cause anxiety? Low vitamin D, low vitamin B12, and iron deficiency have the strongest links to anxiety symptoms, with weaker evidence for magnesium and omega-3 fatty acids. But "linked" is doing a lot of work in that sentence. A deficiency can produce symptoms that feel exactly like anxiety, and it can make an existing anxiety disorder harder to treat. It rarely explains the whole picture on its own.
Below, we walk through each nutrient, the blood tests that check for them, and the point where anxiety needs more than a nutrient fix.
Can a vitamin deficiency cause anxiety?
Sometimes, yes. More often, a deficiency and anxiety show up together, and untangling which came first takes a clinician.
The clearest cases are deficiencies that change how your body feels from the inside. Low B12 can cause fatigue and heart palpitations. Iron deficiency anemia can leave you tired, dizzy, and short of breath. And a racing heart with no obvious cause is one of the fastest ways to set off anxious thinking. In those cases, correcting the deficiency can ease symptoms that looked psychiatric.
Most studies in this area, though, are observational. They find that people with anxiety tend to have lower levels of certain nutrients. That pattern can mean the deficiency raises anxiety risk. It can also mean anxiety changes how people eat, sleep, and spend time outdoors. Both are probably true at once.
The nutrient deficiencies most linked to anxiety
Vitamin D
Vitamin D is the nutrient people search about most, and the evidence is real but modest. A 2022 review in Current Nutrition Reports concluded that low vitamin D levels are associated with more symptoms of depression and anxiety, and the authors argued for checking levels when planning treatment for these conditions.
So can low vitamin D cause anxiety? It can contribute. What it can't reliably do is reverse anxiety once levels are topped up. A systematic review of 20 randomized trials with 2,256 participants found that, for anxiety specifically, the trial evidence was limited to vitamin D given alongside standard treatment. The NIH Office of Dietary Supplements goes further on mood: it notes that clinical trials show vitamin D supplements do not prevent or ease symptoms of depression.
People also ask whether low vitamin D can cause panic attacks. We haven't found good research that tests that question directly. If you're having panic attacks, they deserve an evaluation of their own.
Vitamin B12 (and folate)
B12 keeps nerve cells and red blood cells healthy, and a deficiency can take years to show up because the body stores so much of it. According to the NIH, B12 deficiency affects between 3% and 43% of older adults. Symptoms include tiredness, weakness, heart palpitations, numbness or tingling in the hands and feet, depression, confusion, and poor memory. People who eat few or no animal foods and people taking metformin are also at higher risk.
In the Hordaland Homocysteine Study of 5,948 adults, published in Archives of General Psychiatry in 2003, neither low B12 nor low folate was related to anxiety. Elevated homocysteine, a marker of impaired B-vitamin metabolism, was linked to depression instead. If you've read about folate in connection with the MTHFR gene and mental health, this is the same pathway.
That doesn't make B12 irrelevant. A true deficiency produces physical symptoms that feed anxiety, and it needs treatment regardless. But low B12 is a better explanation for fatigue, numbness, and low mood than for anxiety alone.
Iron
Iron deficiency anemia has one of the more striking data sets. A Taiwanese national study published in BMC Psychiatry in 2020 followed 19,397 adults with iron deficiency anemia and 38,794 matched adults without it. The anemia group had a 47% higher risk of a new anxiety disorder diagnosis (adjusted hazard ratio 1.47), after accounting for age, income, and other health conditions. Among people with anemia, those who received iron treatment had a lower risk of psychiatric disorders overall.
Heavy menstrual periods, bleeding in the digestive tract, and conditions such as celiac disease that block absorption all raise the risk. The NHLBI lists fatigue, dizziness, shortness of breath, and cold hands and feet among its symptoms. Several of those feel like anxiety from the inside.
Magnesium
Magnesium gets a lot of attention online. The research is thinner than the hype. A 2017 systematic review of 18 studies found hints of benefit in people already prone to anxiety, but the authors rated the quality of the evidence as poor. Many people in the U.S. eat less magnesium than recommended, yet the NIH notes that low intake in the short term usually doesn't produce obvious symptoms.
Omega-3 fatty acids
Omega-3s are fats, not vitamins, but they belong on this list. A 2018 meta-analysis in JAMA Network Open pooled 19 trials with 2,240 participants and found a modest reduction in anxiety symptoms with omega-3 treatment. The effect was clearer in people with a diagnosed condition and at doses of at least 2,000 mg a day. Lower doses didn't separate from control groups.
What vitamin deficiency causes fatigue and anxiety?
If tiredness and anxiety arrived together, three deficiencies are worth ruling out first: iron, vitamin B12, and vitamin D. Iron and B12 deficiency can both cause anemia, which leaves you exhausted, short of breath, and aware of your own heartbeat. That combination can feel like constant low-grade panic.
Fatigue is also one of the core symptoms of generalized anxiety disorder itself. The NIMH criteria include difficulty controlling worry on most days for at least six months, plus at least three of: restlessness, fatigue, trouble concentrating, irritability, muscle tension, or sleep problems. Sometimes tiredness is a deficiency. Sometimes it's the anxiety. Often it's both, which is why testing matters more than guessing.
Other medical causes that look like anxiety
Nutrients aren't the only physical explanation. An overactive thyroid is the classic example. The NIDDK lists nervousness, irritability, a rapid or irregular heartbeat, trouble sleeping, fatigue, and shaky hands among the symptoms of hyperthyroidism. On paper, that's almost a description of an anxiety disorder.
A good evaluation checks for these physical causes first. Finding one doesn't end the conversation, though: a thyroid problem or a deficiency can sit alongside a real anxiety disorder.
How nutrient deficiencies are tested
A clinician who suspects a deficiency will usually order blood work. For the nutrients in this article, that often means:
- Complete blood count (CBC), iron, and ferritin to look for iron deficiency and anemia. The NHLBI describes this as the standard workup.
- Vitamin B12, sometimes with folate, especially in older adults, people who eat little or no animal food, and people taking metformin.
- 25-hydroxyvitamin D, the form of vitamin D measured in blood.
- Thyroid function tests when symptoms overlap with hyperthyroidism.
Food first, and what to know about supplements
Most of these nutrients come from a varied diet. Oily fish provides omega-3s and some vitamin D. Meat, fish, eggs, and dairy are the natural sources of B12. Red meat, beans, and leafy greens supply iron. Nuts, seeds, whole grains, and leafy greens are good sources of magnesium.
Supplements are a different matter, because more is not automatically safer:
- The NIH sets the upper limit for vitamin D at 4,000 IU a day for adults. Very high blood levels can cause nausea, confusion, kidney stones, and an irregular heartbeat.
- High doses of vitamin B6 taken for a year or longer can cause severe nerve damage.
- High magnesium intake from supplements can cause diarrhea, nausea, and cramping.
- Treatment for a confirmed deficiency, such as iron or B12, is dosed to the test result and rechecked. That's a medical decision, not a guess.
When anxiety needs more than a nutrient fix
Correcting a real deficiency can take the edge off. It won't resolve an anxiety disorder that has its own momentum. Anxiety that persists after your levels are back in range, that keeps you from working or sleeping, or that travels with low mood is a signal to get a full psychiatric evaluation. Anxiety and depression overlap often, and we've written about how anxiety and depression feed each other. Sudden waves of fear with a pounding heart may also be panic attacks that don't always look like panic attacks.
This is where integrated care makes a difference. At Amae Health, our care teams bring psychiatrists, therapists, primary care physicians, and dietitians under one roof. Lab work, physical health, nutrition, and psychiatric treatment are read together, by people who talk to each other. A low ferritin result and a panic disorder diagnosis don't get handled by two clinicians who never compare notes.
Frequently asked questions
What vitamin deficiency causes anxiety and depression?
Low vitamin D is associated with both anxiety and depression in observational research. Low B12 and folate are more consistently linked to depression than to anxiety. Iron deficiency anemia is associated with a higher risk of both diagnoses.
Can low B12 cause anxiety?
A B12 deficiency causes fatigue, palpitations, numbness, and low mood, all of which can feel like anxiety or make it worse. A large population study found no direct link between low B12 levels and anxiety itself. A deficiency still needs treatment.
Can low vitamin D cause panic attacks?
There's little research that tests this directly. Low vitamin D is linked to anxiety symptoms in general, but panic attacks have many causes and deserve their own evaluation.
How long does it take to feel better after correcting a deficiency?
It depends on the nutrient, how low your levels were, and what caused the deficiency. B12 deficiency can take years to develop, so recovery isn't always quick either. Your clinician will usually recheck levels after treatment to confirm they've come up.
Should I get tested if I have anxiety?
If your anxiety came with fatigue, palpitations, dizziness, or numbness, or if you have a risk factor such as a plant-based diet, heavy periods, or metformin use, blood work is a reasonable part of an evaluation. A clinician can decide which tests fit your history.
Key takeaways
- The nutrient deficiencies most linked to anxiety are vitamin D, vitamin B12, and iron. Evidence for magnesium and omega-3s is weaker.
- Most of the research shows association, not proof of cause. Supplements haven't been shown to treat anxiety disorders on their own.
- Fatigue plus anxiety is a good reason to check iron, B12, vitamin D, and thyroid function.
- Anxiety that lasts after deficiencies are corrected needs psychiatric care, not more supplements.
If anxiety is wearing down your days, or someone you love is living with severe anxiety alongside depression, you don't have to sort out the physical and psychiatric pieces on your own. See how our integrated outpatient clinics work, or request an intake appointment and our team will walk you through what the first visit includes.