Methylcobalamin (often 1000 mcg) can be taken safely in many cases and may help if your symptoms are due to vitamin B12 deficiency, which can sometimes contribute to nerve issues and low mood. However, it is not a primary treatment for depression or tinnitus unless a deficiency is confirmed. It?s better to check your B12 levels and consult a doctor before starting, so you get the right treatment for the actual cause.