This could suggest though that a female black widow could be close by so please do not approach one if you see it. The females will have a red hourglass shaped abdomen. It will sometimes have a pair of red spots or it could have no markings at all. Seek expert advice immediately and do not attempt to move the spider yourself as the consequences could be very serious for you and your health.
There is a chance it may not be a black widow as there are so many different species of spiders, all with different characteristics. As there is still a chance it could be a black widow, it is best not to take any chances and to get it checked out by an expert in your local area.
Adult male black widows are not as big as their female counterparts. In fact they are only about a quarter the size. They are usually grey or black with a yellow or white marking on their abdomen.
By getting in touch with a local expert they will be able to look at the spider to identify what exactly it is. They may look at any webs they may have spun, the position of the marking on their back and their size.
By only providing a small description of the spider you have at home, it may very difficult to give an exact and accurate answer. There are too many spider species in the world to give a definite answer without taking things such as the abdomen, general size and other issues into consideration. It may be better to seek expert advice if you are concerned.