Well, we do age, and with age comes changes in metabolism.

I have a few questions UTGrad...

1) when you have the tingling etc, is it all the time, or only when you run, or say are hungry? Does it go away with food consumed?

2) do you smoke and/or drink alcohol?

3) what is your diet like? Running puts a huge load on magnesium and B6. Most Americans do not consume enough magnesium daily to match the RDA for it. Magnesium is involved in the actions for energy production in the mitochondria.

4) I do think there is a possibility for you that your exercise regimen has reached some upper limit of tolerability. People all vary in how they can sustain stressful exercise, and as we age the mitochondria may be aging too. We have had younger PNers here who were pushing their limits. One fellow had extreme pain in his palms and wrists, and we finally found it was due to his pushups. He stopped them for a long period and his pain stopped. Pain is a warning sign, and running in the presence of nerve symptoms is not a good idea. Could you walk instead, and cut down from 4 miles walking to one?

5) a good thorough evaluation with Xrays of your feet might be in order at a podiatrist. Too tight of lacing of your shoes can compress the nerves in your instep and create compression symptoms, which may linger throughout the day do to the repeated daily running.

6) do you take supplements? Energy drinks, nutrition bars? Many cereals today are fortified with B vitamins. If you take supplements and took them the day of your blood work, the B12 and B6 would show a false elevation. If so 500pg/ml for B12 as a false elevation is not a good result. The B6 may be also due to consumption of B6 that you didn't pay attention to. It is also not a common test, and the labs may have used old calibration material and the test may be inaccurate as a result. The ranges used by labs were made from volunteers who were NOT using vitamins or fortified foods at the time of the testing.