1. An apparatus for indicating a health-related condition of a subject, wherein the health-related condition is a diabetes-related or glucose-related or insulin-related metabolic condition, comprising: an input interface for receiving a raw sequence of samples of a first biological quantity derived by a first measurement method, the first measurement method being an invasive measurement and having a first impact on the subject, and for receiving a raw sequence of samples of a second biological quantity derived by a second measurement method, the second being a non-invasive measurement and having a second impact on the subject, the biological quantities having a useful variation and a non-useful variation; wherein the first biological quantity gives a more accurate indication of the health-related condition of the subject than the second biological quantity, wherein the first biological quantity and the second biological quantity have a correlation to the health-related condition of the subject, and wherein the second impact is smaller than the first impact; a predictor for providing, for a certain time, for which no sample for the first biological quantity exists, an estimated value of the first biological quantity as a predicted sample using samples for the second biological quantity and, as far as available, samples for the first quantity; a filter for filtering a sequence having samples of the first biological quantity and at least one predicted sample, the filtered sequence having a useful variation and a reduced non-useful variation compared to the sequence before filtering, and an output interface for outputting at least an increase indication, a decrease indication or a remain unchanged indication as a trend of the data, the trend being representative to a useful variation of the health-related condition of the subject.