Brief Answer:
it can be circulation or the nerves

Detailed Answer:
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Tingling sensations are a type of paresthesia which is essentially tingling, burning , prickling or any abnormal sensations felt in a persons skin.

It can be related either to the nerve or blood supply to the particular.

Blood: if the blood supply to an area is compromised , it can result in abnormal sensations in that particular are. In terms of the fingers compromised blood supply can occur in persons with a history of joint disease where the bone may be compressing the nerve for example arthritis, fractures, tumors or lesions on the bone, dislocation

Nerve: Abnormal function of the nerves can also result in tingling sensation. This can occur if (1) a nerve is compressed , in the case of the fingers this can occur if there is anything compressing the nerves coming from the neck such as cervical rib.
rheumatoid arthritis

(2) endocrine conditions such as diabetes, abnormal thyroid hormone levels

(3) vitamin deficiency particular vitamin b 12

To determine the exact cause of the tingling , your doctor will take a thorough history to find out which fingers are involved and whether it is the palmar aspect or the other side of the hand.
This is important because it indicates which nerves are involved, certain nerve supply particular aspects of the arm and hand.

Examination would be able to determine if there is adequate circulation.

Blood tests checking for diabetes, thyroid hormone levels, vitamin b12 and possibly to check for RA if there are any other symptoms.

Treatment would depend on the cause found.

I hope this helps, feel free to ask any additional questions

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