There are several relatively simple lifestyle changes a woman can make that might elevate T levels. Most obviously, if a woman believes her birth control pills are causing a problem and she feels she can adjust to a different type of birth control, she might stop using them (if indeed she's using them exclusively to prevent conception). She might also reevaluate her need for any of the various medications I mentioned, and perhaps seek alternatives that might not affect testosterone levels. For instance, there's some evidence that the antidepressant wellbutrin actually increases libido, but whether it helps the sex mojo through raising T levels or by some other mechanism isn't well understood.
In men, low testosterone levels in the body can be supplemented by hormone replacement with testosterone. Testosterone replacement therapy can be prescribed as an intramuscular injection usually given on a biweekly basis; as a patch or gel placed on the skin, or as putty that is applied to the gums of the mouth. Each of the treatments has its risks and benefits. The decision as to which form of testosterone to use depends upon the clinical situation. Discussions between the patient and health care professional often helps decide which medication to use.
In the United States there are currently no preparations that are FDA approved for testosterone replacement for women.