By Jessica Yacques, PMHNP-BC, FNP-C, Two Rivers Integrative Health. Reviewed by Rebecca Moyes, PMHNP-BC · November 2026
Yes, sometimes. Low levels of iron, vitamin B12 or vitamin D can contribute to depression, anxiety, fatigue and brain fog, and the symptoms can look a lot like a primary mood disorder. Those three are the deficiencies I find most often. A simple blood test can check. Finding and treating a deficiency doesn't replace mental health care, but it is an important part of the whole picture.
There are so many things that can drive depression: neurotransmitters, yes, but also inflammation, autoimmunity, nutrition, circadian rhythm, genetics and trauma. My job is to look at all of it and fine-tune from there.
Which deficiencies can affect mood?
These are the nutrient deficiencies I look for most often when someone comes in with depression, anxiety or exhaustion.
| Nutrient | Symptoms it can contribute to | Who is more likely to run low |
|---|---|---|
| Iron | Fatigue, low energy, low mood, poor concentration, restlessness | People with heavy periods, pregnancy, vegetarian diets, blood loss or malabsorption |
| Vitamin B12 | Depression, fatigue, irritability, memory and concentration problems, numbness and tingling | Vegetarians and vegans, older adults, people taking metformin or acid-reducing medication, people with absorption problems |
| Vitamin D | Low mood and fatigue, especially in darker months | People with little sun exposure, darker skin, or limited dietary sources; common in the Pacific Northwest winter |
How would you know if a deficiency is part of the picture?
You can't tell from symptoms alone, because the symptoms overlap so much with depression and anxiety. What makes me suspect a deficiency is a patient's dietary habits, gastrointestinal problems, and vague symptoms like fatigue, brain fog and headaches. Heavy periods, or depression that hasn't responded the way we'd expect to treatment, are worth checking too. That is why I ask a ton of questions and look at the whole body, not just the mood symptoms.
Should you get tested?
If you are struggling with depression, anxiety or fatigue, it is reasonable to ask about lab work. Commonly checked labs include a complete blood count, iron studies including ferritin, vitamin B12 and other B vitamins, and vitamin D, along with thyroid tests, since thyroid problems can also drive mood symptoms.
At my first visit with a patient, I take a full, head-to-toe history, usually order bloodwork, review it, and fine-tune from there. I keep labs within the budget a patient gives me. I guide patients on how to get out-of-pocket estimates from their insurance company, adjust the lab order to fit the budget, and start with the basics, expanding later if needed.
Will fixing a deficiency fix my depression?
Sometimes treating a deficiency makes a real difference. Often it is one piece of a larger plan that may also include therapy, medication and lifestyle changes. A thorough workup sometimes uncovers a contributing condition; it doesn't promise one.
Please don't stop or change any psychiatric medication on your own because of a lab result. Medication changes should always happen with your prescriber. And I'm not anti-medication at all. The goal is more tools, not fewer.
Should I just take supplements?
It's better to test first. Some supplements can cause problems at high doses, iron, vitamin D and B6 in particular, and taking supplements before testing can make results harder to interpret. Testing tells us what you actually need, so we can be specific.
What else can mimic depression or anxiety?
Nutrient deficiencies are one of several groups of physical conditions that can drive mental health symptoms. Others include thyroid and other hormone problems, sleep disorders such as sleep apnea, autoimmune and digestive conditions, and side effects or interactions of medications. Looking across all of them is part of how I work.
Frequently asked questions
Can low iron cause anxiety? It can contribute. Iron deficiency often causes fatigue and low energy, and some people notice more anxiety, restlessness or trouble concentrating. A blood test including ferritin can check your iron stores.
Can vitamin D deficiency cause depression? Low vitamin D is linked with low mood in research, though whether supplementing helps depression is still being studied. It is easy to test and worth knowing, especially through an Oregon winter.
Can B12 deficiency cause depression? Yes, B12 deficiency can cause depression, fatigue and memory problems, and it is more common in vegetarians, vegans, older adults and people taking certain medications.
What is functional or nutritional psychiatry? It is an approach that looks at physical contributors to mental health, such as nutrition, inflammation, hormones and sleep, alongside the usual tools of psychiatry, like therapy and medication.
How do I get started? Call (971) 368-1045 or use the contact form. Ask us about fees before you book; a Good Faith Estimate is available under the No Surprises Act.
We will figure this out
If you've been struggling and something still doesn't add up, come get the whole picture looked at. I will listen to you. You will not feel judged. You will be validated. We will figure this out.
Sources
National Institutes of Health, Office of Dietary Supplements, Iron fact sheet. https://ods.od.nih.gov/factsheets/Iron-Consumer/
NIH Office of Dietary Supplements, Vitamin B12 fact sheet. https://ods.od.nih.gov/factsheets/VitaminB12-Consumer/
NIH Office of Dietary Supplements, Vitamin D fact sheet. https://ods.od.nih.gov/factsheets/VitaminD-Consumer/