Insulin goes bad about 30 days after first use. Pretty much all diabetics need to buy a vial or two every month, no matter if you&#x27;ve used it all or not.<p>Think of it like keeping milk stocked in your fridge. Even if you spread it out to last more than a month, the remaining half will go bad before you got to it.<p>So although changing diet and increasing physical activity may reduce insulin requirements in both type 2 and type 1 (as several people have anecdotally shared here), you can see how it doesn&#x27;t avoid buying insulin every month.