Feeling drained no matter how much you sleep? Struggling to concentrate during the day or feeling more anxious than usual? While stress, poor sleep, and underlying health conditions can all contribute to these symptoms, doctors say certain vitamin deficiencies may also play a role.
Although supplements aren’t a cure-all, identifying and correcting a deficiency can help improve energy levels, cognitive function, and overall well-being. If you’re experiencing persistent fatigue, brain fog, or anxiety, it’s important to speak with your healthcare provider before starting any new supplement regimen. Here are three vitamins doctors commonly say are worth checking.
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1. Vitamin B12
Vitamin B12 is one of the most important nutrients for energy production and nervous system function. A deficiency can leave you feeling exhausted, mentally sluggish, and even anxious.
“B12 is required for red blood cells to form and for cellular energy production,” registered dietitian and molecular biologist Andreea Nitescu, says.
According to healthcare professionals, low B12 levels may contribute to:
- Persistent fatigue
- Brain fog
- Difficulty concentrating
- Tingling or numbness in the hands and feet
- Mood changes
Older adults, vegetarians, vegans, and people with digestive conditions that affect nutrient absorption are at a higher risk of deficiency. Foods rich in B12 include salmon, tuna, eggs, dairy products, beef, and fortified cereals.
2. Vitamin D
Often called the "sunshine vitamin," vitamin D plays an important role in immune function, bone health, muscle strength, and even mood regulation.
Research has linked low vitamin D levels with:
- Fatigue
- Low mood
- Difficulty focusing
- Increased risk of anxiety and depression
Because many people spend much of their time indoors or live in areas with limited sunlight, vitamin D deficiency is relatively common. In addition to safe sun exposure, vitamin D can be found in fatty fish, fortified dairy products, egg yolks, and fortified plant-based milks.
3. Folate (Vitamin B9)
Folate helps your body produce healthy red blood cells and supports normal brain function. When levels are low, some people may experience:
- Low energy
- Trouble concentrating
- Irritability
- Memory difficulties
- Mood changes
Leafy greens, lentils, beans, asparagus, avocados, and fortified grains are excellent dietary sources of folate.
The bottom line
Fatigue, anxiety, and poor concentration can have many causes, including thyroid disorders, anemia, chronic stress, poor sleep, medication side effects, and mental health conditions. Because these symptoms overlap with numerous medical issues, it's important not to self-diagnose.
If you've been feeling unusually tired or mentally foggy for several weeks, your healthcare provider can perform blood tests to determine whether you have a vitamin deficiency and recommend the most appropriate treatment. Correcting a deficiency may help restore your energy and improve your ability to focus—but only if it's truly the underlying cause.
