Even if your hair is thin all over how likely is it that you can give an appearance of thicker hair by moving some hair from less noticeable locations to the front?
This question covers a lot of territory:
1- If there is generalized thinning over the entire head and you are a male and the thinning is in the side and back of your head as well, you might have a condition called Diffuse Unpatterned Alopecia (DUPA). This condition is not good news, and these patients can not undergo a hair transplant as there is a poor donor area and therefore the doctor can not move enough good quality hair to cover the thinning area. Scalp micropigmentation (SMP) on the other hand, may be a good alternative (see: scalpmicropigment.com).
2- If there is generalized thinning over the entire head and you are a female and the thinning is in the side and back of your head as well, you will not be a candidate for hair transplantation as the transplanted hair will have poor growth. Again as I said in #1 above, Scalp micropigmentation (SMP) on the other hand, may be a good alternative
3- If you are a male and you have thinning on the front, top and/or crown area and you are under 30 years old, the first treatment course we would be to try finasteride (Propecia) and give you a year to see if some of the hair thinning stabilizes or possibly reverses in some of these areas. If you stabilize or reverse the thinning process, hair transplants can be planned at that point in time if appropriate, however, you must work out the hair supply/demand issues with your doctor. Thinning in men evolves into balding and hair transplants do best in treating balding. When we perform a hair transplant on a young man, we advise the patient to use the drug finasteride to minimize any shock loss from the hair transplant surgery.
4- For women who do not bald but have thinning and a healthy donor area, the amount of hair that needs to be transplant may be limited by the size of the thinning area and the amount of hair one can transplant in a single session. If the thinning is great, the benefits of even a large hair transplant (say~ 2500 grafts) might not be enough to make an appreciable difference. In these situations, I might transplant a female in particular area (like the frontal area to strengthen the hairline or a central or right/left part to make the area look fuller). In this way there can be a partnership between styling and transplants. This is difficult to explain but worth a consultation with an expert in this field.
Most important, there is a balance between the demand for hair and the supply of hair as the doctor moves it around.