Female hair transplant: Do you need to shave all head? And what medication could be used for hair loss prevention?

You do not need to shave to have a hair transplant procedure.  Some doctors may require it but it is not mandatory.

If you transplant is done as a strip procedure, only the hair in the strip is trimmed so the hair above and below cover the incision.  The recipient area does not need to be shaved.Options to prevent hair loss and maintain your hair include maser therapy, minoxidil (Rogaine) and platelet-rich plasma.  Depending on the cause and your medical history, medications such as spironolactone or finasteride (Propecia) may be indicated. 

I perform a "Shave-less" FUE hair transplant procedure on ALL of my female transplant patients.  It is performed by trimming the hairs that are going to be grafted for the FUE hair transplant (they have to be cut short for proper extraction) and leaving all of the other hairs in the donor area intact.  This provides full concealment and negates the need for shaving any portion of the head.  A "Shave-less" FUE is a technical procedure and only a few providers offer it to their patients.  
I have found that women are much less inclined to have even a portion of there head shaved and unfortunately will not even consider FUE hair transplantation because of it.  If you are not interested in a strip harvest which leaves a linear scar, then look into a "Shave-less" FUE approach.

Thank you for question. You have been diagnosed with female pattern hair loss, and are now asking if a hair transplant requires you to shave your head, and what medications can be used to prevent further hair loss.
I can help guide you with this question, without the benefit of a physical exam, or any images of your hair loss. I can help guide with you with this, even without a physical exam and more details about your hair loss situation. I’m Dr. Amiya Prasad. I’m a Board Certified Cosmetic Surgeon and Fellowship Trained Oculoplastic Surgeon. I’ve been in practice in Manhattan and Long Island for over 20 years. I’ve been performing hair transplants since the beginning of my practice. I’m also the founder of TrichoStem Hair Regeneration Centers, which employ a non-surgical pattern hair loss treatment for men and women using PRP and extracellular matrix since 2011, which pioneered a new classification of hair loss treatment.
You didn’t indicate if your doctor actually recommended a hair transplant, but I assume they did not because you are asking about shaving your head. Before entertaining that question, it’s important to inform you that for the vast majority of female pattern hair loss patients, hair transplants are not recommended. Female pattern hair loss usually follows a diffuse pattern, meaning hair thinning occurs throughout the whole scalp. In hair transplants where the hair implanter basically small incisions in the scalp, the area where the hair is transplanted should not be near native hair. If there is native hair nearby, the implanter can stab nearby hair follicles, causing damage and permanent loss of those hair follicles called collateral loss. Since hair is thinning through the whole scalp, there is no safe way to transplant hair on most cases of female pattern hair loss. Most female hair transplants are hairline lowering procedures where there is no existing hair on the hairline, or transplanting hair on a widened hair part where there is little to no existing hair. In cases where hair transplant is an option, the whole scalp doesn’t need to be shaved, just the donor area at the back of the head where hair grafts are taken.
We treat our female pattern hair loss is with an injectable treatment called Hair Regeneration to thicken thinning hair and stimulate hair follicles that aren’t growing to grow new hair. This treatment is made up of platelet-rich plasma, or PRP, which are the concentrated wound healing and growth factors present in your own blood; and an advanced wound healing material called extracellular matrix. This treatment has shown visible results in thicker hair and increased hair coverage and density in over 99% of our male and female pattern hair loss patients. Each treatment is customized for the individual patient based on age, gender, age of onset of hair loss, degree of hair loss, other medical factors, and other treatments already taken. The treatment can last 3-5 years or longer, and the majority of patients only have one treatment session.
There are fewer hair loss treatments available for women, since most women can’t have hair transplants, and the drug finasteride is exclusively used by men to block the formation of the hormone DHT, which women don’t have in significant amounts. Minoxidil can be used by women, but this treatment does not thicken thinning hair, but rather appears to delay the hair shedding phase, and extends the growth phase so you appear to have more hair on your head. However, minoxidil has to be used continuously to prevent a sudden shed of hair, and the effects can wane even if used regularly. Scalp injections of PRP alone are an increasingly popular treatment, but this treatment needs several sessions to stimulate hair growth, and growth is usually short-term, so the procedure needs to be done continuously and indefinitely.
I suggest you meet with doctors who specialize in hair loss treatment, and discuss what I mentioned regarding hair transplants for women, and other treatment options. A treatment like Hair Regeneration can be the most effective and convenient option available, so do more research about similar treatments, and think about treating thinning hair rather than transplants. I hope you found this information helpful. Thank you for your question.

Shaving the head with a Strip surgery is not necessary as the recipient hair can be placed between your existing hairs.  In my experience only 20% of women are good candidates for hair transplants. I would have to see photos of your to give you more information

if your doctor is doing the strip method, then there is no shaving required. You hair loss specialist should give you recommendations for medical hair treatments depending on the cause of your hair loss, degree of your hair loss and your concerns.