Q: I have epilepsy and was well-controlled on Keppra and Topamax for years. When I was switched to generic Keppra (levetiracetam) without realizing it, I had several seizures in two weeks. I fell down stairs and had a seizure while cooking.

My doctor has switched me to Keppra XR, which currently has no generic. My epilepsy is controlled now, but what will I do when the insurance company insists on the generic again? I will have to stop driving and become housebound.

A: We have heard from many others who have experienced serious symptoms when their insurance company forced them to switch to a generic drug. We recently received this advice from a pharmacist: “You must ask your physician to complete a letter of medical necessity that documents how long the physician has been treating the patient, what therapies have been used and failed, and what therapies are working with minimal side effects.

“Expect the insurance company to fight, but administrative clerks are not medically savvy. Don’t be afraid to use the magic word ‘lawsuit.’ I have called physicians and helped many patients challenge their insurance companies. Plenty of success stories and plenty of lives saved!”

Anyone who would like our Guide to Saving Money on Medicines with tips on using generic drugs wisely may send $3 in check or money order with a long (No. 10), stamped (66 cents), self-addressed envelope to: Graedons' People's Pharmacy, No. CA-99, P.O. Box 52027, Durham, NC 27717-2027. It also can be downloaded for $2 from our website.

Q: You have written about the sorry state of public restrooms and wet toilet seats. You said to worry more about bacteria on flush handles or doorknobs, but what about jock itch? Women get it just as bad as men, and it sure can be catching from a wet or even a dry toilet seat.

A: Jock itch is known medically as Tinea cruris. It is a skin infection caused by fungi such as Candida, Epidermophyton or Trichophyton.

There is a shocking lack of research on how people catch jock itch. No studies show that toilet seats are culprits in transmitting this infection. Nevertheless, there is a possibility that contact with a contaminated toilet seat or even a locker-room bench might spread the fungus from person to person. Using a toilet-seat cover might be a reasonable precaution.

Q: My doctor just told me that I am borderline diabetic, with a blood-sugar reading of 115. He also said my vitamin D levels were very low. He recommended 5,000 IUs of vitamin D-3 daily for several months. Then he wants to measure my fasting blood sugar and vitamin D levels again. Why would vitamin D have anything to do with diabetes?

A: Vitamin D affects genes that direct a surprising number of activities in the body (PLOS One, March 20, 2013). Swedish researchers have found that people with prediabetes are less likely to develop full-blown diabetes if they have high vitamin D levels (Diabetologia, June 2012).

We haven’t seen any studies that show taking vitamin D supplements can normalize blood sugar, but it is certainly worth a try. We hope you’ll let us know the results of your one-person experiment.

Q: I’ve been sleepwalking and having really bad dreams for two years. It finally hit me that this all started soon after I started taking Toprol.

A: Toprol (metoprolol) and other beta blockers (atenolol, propranolol) can cause nightmares and disturbed sleep for some people.

In their column, Joe and Teresa Graedon answer letters from readers. Email them on their website. Their newest book is "Top Screwups Doctors Make and How to Avoid Them."