It really depends. Remember that the two most important factors for getting into medical school are GPA and MCAT score. Having a double major will not increase either of these factors.
What can help is if your double major paints a better picture of you as an applicant. For example, if you double major in a science and a humanities discipline, it can make medical schools believe you are a more well-rounded student then let’s say, someone who is just a science major. A well-rounded student is something all medical schools want. It also makes you unique because few pre-med students are double majors. Medical schools like unique students because it adds to the diversity of their student population. Lastly, it can make you seem more academically prepared than your peers. Medical schools need to know if you can handle the course load of medical school before they accept you.
However, having a double major will not help leverage a lower GPA and/or a lower MCAT score. In fact, medical schools will probably question your motive for having a double major if you have low academic scores. They will wonder why you did not just major in one discipline if you could not handle two. It is much more likely for medical schools accept an applicant who has a high GPA with one major, then an applicant with a lower GPA but two majors.
Our advice is that you ask yourself one important question before you decide to double major: Do you think your GPA and your MCAT scores are going to be lower due to the course load of a double major? If you answer yes, it is probably best you stick to one major. The benefit of having a double major will not be worth the cost of having a lower GPA and/or lower MCAT score. However, if you think your academic scores will not suffer, you can double major because it can only help your application.