Hello. Thanks for your question. I am a board certified neurologist in the U.S. I will be happy to help.
With the numbness you are describing, it would be most likely that you are dealing with a condition called peripheral neuropathy, which is a dysfunction of the nerves that are the furthest distance away from the spine. Hence, the toes and fingers can become affected most often by this type of condition. Another possibility could be that there are pinched nerves in your neck and back causing the finger and toe numbness, or that there could be a compression of the nerves in the wrist for example (which could lead to finger numbness in the case of carpal tunnel syndrome).
Assuming the symptoms are due to peripheral neuropathy, indeed diabetes and B12 deficiency are worth looking for. However, there are many other conditions that can lead to neuropathy. You will certainly benefit from seeing a neurologist if you have not done so to further investigate your symptoms and to have a complete history and examination performed. Other blood tests that can be useful in neuropathy evaluations can include folic acid levels, thyroid studies, screening for kidney function, a serum protein electrophoresis (evaluates proteins in the blood), and possibly other tests such as syphilis, HIV, hepatitis, etc. The list of possible causes of neuropathy is quite long, and therefore a trained neurologist would need to assist you in trying to find a cause.
Other than blood testing, a procedure called a nerve conduction study/EMG exam can be performed in appropriate cases to help identify neuropathy and rule out other conditions such as carpal tunnel syndrome, or issues affecting the nerve roots in the neck or low back.
Hopefully this has been helpful to you. Please let me know if there are more questions. If this has been helpful, please rate me highly. Bonuses always appreciated. Best of luck.
You are very welcome. Please consider consulting with a neurologist. This will be your best step in trying to get to the bottom of why your symptoms are occurring. They will then be able to determine appropriate testing to hopefully provide you a diagnosis and proper treatment.