1. An intranasal composition comprising methylcobalamin, atleast one gelling agent and optionally a permeation enhancer selected from lecithin and di-ethylene glycol monoethyl ether, wherein the composition forms in-situ gel after intranasal administration.
2. The intranasal composition according to claim 1, wherein the composition comprises methylcobalamin, at least one gelling agent and a permeation enhancer selected from lecithin and di-ethylene glycol monoethyl ether.
3. The intranasal composition according to any of the preceding claims, wherein the composition comprises about 0.01 to about 0.45% w/v of methyl cobalamin.
4. The intranasal composition according to any of the preceding claims, wherein the composition comprises about 0.1-1% w/v of gelling agent.
5. The intranasal composition according to any of the preceding claims, wherein the composition comprises about 0.1-1% w/v of permeation enhancer.
6. The intranasal composition according to claim 4, wherein the gelling agent is gellan gum.
7. The intranasal composition according to any of the preceding claims, wherein the composition further comprises excipients selected from thickening agent, humectant, preservative, flavoring agent and vehicle.
8. The intranasal composition according to claim 7, wherein the amount of thickening agent present is about 0.1% to about 1% w/v of the composition.

9. The intranasal composition according to claim 7, wherein the amount of
humectant present is about 1% to about 5% w/v of the composition.
10. The intranasal composition according to claim 7, wherein the amount of preservative present is about 0.01 to about 1% w/v of the composition.
11. The intranasal composition according to any of the preceding claims, wherein pH of the composition ranges from 4 to 5.5.
12. The intranasal composition according to any of the preceding claims, wherein composition is administered once weekly.
13. The intranasal composition according to any of the preceding claims, wherein the composition comprises about 2500 microgram/ml of methylcobalamin.
14. The intranasal composition according to claim 13, wherein an intranasal administration of 100 microliters of the composition to each nostril of human, provides and maintains mean plasma concentration of cobalamin of about 200pg/mL or more for at least 7 days.
15. A method of treating vitamin B12 deficiency by intranasally administering composition comprising methylcobalamin, atleast one gelling agent and optionally a permeation enhancer selected from lecithin and di-ethylene glycol monoethyl ether, wherein composition forms in-situ gel after intranasal administration.
16. Use of intranasal composition comprising methylcobalamin, atleast one gelling agent and optionally a permeation enhancer selected from lecithin and di-ethylene glycol monoethyl ether, for the treatment of Vitamin B12 deficiency wherein, wherein composition forms in-situ gel after intranasal administration.