Getting sick in a far away foreign land is a tough cookie.

Risk Management is the prudent thing to do.

Medical Treatment in India is extremely affordable but still you should have insurance more for serious stuff like Evacuation after a serious fall.

Bug spray containing at least 30% DEET (try deep woods type from camping store) is advisable in Delhi area even at airport. (may not be needed in Leh) Malarone is Malaria prevention drug. There is no quick cure for Dengue - only prevention.

You may want to look into Acetazolamide for altitude sickness.

My personal preference is to avoid ANY meat (just to be safe) and avoid fruits/salads even at 5 star hotels. Only recently cooked HOT items. Plenty of freshly cooked safe vegeterian food choices should be available. Anyone insisting on eating Western dishes in rural India deserves the gastro punishment one is likely to get.

Tylenol, Ibuprefen, Immodium, Lots of Tums, Cough-drops, Band-Aid, Neosprin, Cortizone, Ammox or Zithromax (antibiotics are available in India over the counter at fraction of a cost (many made by same US/Euro companies like Pfizer, Glaxo, Novartis))

It might be helpful to get some historic/political background about the area you are visiting. (Leh is manily Buddhist region somewhat sympathetic to Tibet which has been occupied by Chineese. Luckily it is on the eastern edge of the Jammu-Kashmir state and hence not much affected by Pakistan sponsored terrorism)