unbalanced data set

Dear all, I recently have a data set for pk parameters fitting. The issue is some patients have far more measurement points than others (i.e. a few patients have ~15 points, other patients have only 1 or 2). I speculate in the fitted parameters, those patients with many points would contribute much more than those with less points. Then the population "average" values of fitted pk parameters are not anymore average from all the patients, but more biased to those patients with many points. This is not what I expect. Of course I could take away some points from the patients with many points, in order to be comparable to less-points patients. Then I will be forced to lose some information from the data set. I just wonder are there anyone who have better proposal to solve this problem? I appreciate your help very much! Best regards, Zheng