Prognosis

Vitamin B12 deficiency can cause devastating neurologic disease and severe hematologic disorders. Early diagnosis and prompt treatment may halt progression and reverse neurologic disease.[42] Unfortunately many cases are irreversible and clinical disease may not respond to adequate therapy.[75] Early diagnosis in the near-asymptomatic stage can be critical in preventing permanent neurologic damage.

Megaloblastic anemia

Prompt treatment in patients with megaloblastic anemia due to vitamin B12 deficiency can completely reverse the process. Brisk reticulocytosis occurs within 1 to 2 weeks of initiating treatment.

Subacute combined spinal degeneration

Treatment with vitamin B12 generally leads to clinical (and magnetic resonance imaging) improvement of subacute combined spinal degeneration, and can halt progression of disease. However, only a few patients will have complete resolution with vitamin B12 replacement.[75]

Other neurologic disease

Vitamin B12 treatment may improve peripheral neuropathy.[107][108] Treatment may not completely resolve the process.​​

The potential for improvement of depressive symptoms in patients receiving vitamin B12 supplementation may differ between those with recent onset and those with more advanced neurologic disorders.[109][110]

There is no clear evidence that vitamin B12 supplementation improves dementia or cognitive decline, although some evidence suggests that supplementation with a vitamin B complex or folic acid combined with vitamin B12 may slow progression of cognitive decline and improve symptoms.[7]​[9][111]​[112]​​​​

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