My causes of tingling include B12 deficiency, hypothyroidism, high insulin, magnesium deficiency, calcium deficiency.
Sometimes tingling or numbness in the extremities is a symptom of low Vitamin B-12.
Understand that the "normal" range for B-12 is huge. Many people find they need to be well up towards the top end of the range to feel well. At least for fatigue sysmptoms.