Despite what a number of people think, butter actually contains less than one percent lactose total. According to numerous studies, butter is unlikely to cause any lactose intolerance problems with those who consume it, as long as they do so in moderation. Generally better is eaten in small amounts, so it therefore does not pose a very large health risk as far as lactose is concerned.
When you look at some of the other dairy products there are, comparatively butter has significantly less lactose in it. Those who are simply not sure whether or not they will be able to tolerate the amount of lactose that is in butter should consult with a physician to discuss the risks. Typically though, most people with a lactose intolerance do not have much trouble eating butter or things that were made using butter. More often people who have this problem are affected by milk, ice cream, or other types of dairy products.