What could be causing frequent mood changes?

Reviewed by Yoshinori Abe, MD

Internal Medicine

Frequent mood changes in men can stem from several underlying medical conditions, including low testosterone, vitamin B12 deficiency, and brain tumors. Low testosterone often triggers irritability, depression, and fatigue. Vitamin B12 deficiency can lead to mood swings, cognitive issues, and even symptoms resembling depression or anxiety. Brain tumors, though less common, may cause sudden personality shifts and emotional instability depending on their location.

Because these causes vary widely in severity and treatment, identifying the root of your mood changes is essential. A free, instant, online symptom check can help you evaluate your symptoms in minutes, offer insight into possible conditions, and guide your next steps—whether that's a lifestyle adjustment, lab work, or a visit to a specialist. Don't guess when clarity is just a few clicks away.

Reviewed for medical accuracy: 07/20/2026

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Explanation

Frequent mood changes can happen for several reasons. Low testosterone levels in men may lead to mood swings, irritability, or even depression. Testosterone is a hormone that helps regulate mood, and when levels are low, it can cause emotional changes.

Vitamin B12 deficiency can also lead to mood changes. This vitamin is important for brain health, and not having enough of it can lead to symptoms like mood swings, confusion, or irritability. Ensuring a diet with enough vitamin B12 can help manage these symptoms.

Lastly, brain tumors can affect emotions and personality. Depending on the tumor's location, it can lead to changes in how a person feels or acts. This might include mood swings, personality changes, or difficulty with emotions.

If you or someone you know is experiencing frequent mood changes and it's causing concern, it might be helpful to seek professional advice. To help identify what might be causing your symptoms, try Ubie's free AI symptom checker. For mental health support, you can also visit 988lifeline.org.

(References)

Johnson JM, Nachtigall LB, & Stern TA. (2013). The effect of testosterone levels on mood in men: a review. Psychosomatics, 24016385.
Sahu P, Thippeswamy H, & Chaturvedi SK. (2022). Neuropsychiatric manifestations in vitamin B12 deficiency. Vitamins and hormones, 35337631.
Jenkins LM, Drummond KJ, & Andrewes DG. (2016). Emotional and personality changes following brain tumour .... Journal of clinical neuroscience : official journal of the Neurosurgical Society of Australasia, 26898575.

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