An apparatus for indicating a health-related condition of a subject has ininput interface (20) for receiving a sequence of samples of a first biologicalquantity derived by a first measurement method, the first measurement methodbeing an invasive measurement and having a first impact on the subject, andfor receiving a sequence of samples of a second biological quantity derived bya second measurement method, the second measurement method being a non-invasive measurement and having a second impact on the subject, wherein thefirst biological quantity gives a more accurate indication of the health-related condition of the subject than the second biological quantity, whereinthe first biological quantity and the second biological quantity have acorrelation to the health-related condition of the subject, and wherein thesecond impact is smaller than the first impact, a predictor (30) forproviding, for a certain time, for which no sample for the first biologicalquantity exists, an estimated value of the first biological quantity usingsamples for the first biological quantity and, as far as available, samplesfor the second quantity； and an output interface (25) for outputting theestimated value or data derived from the estimated value so that an foroutputting the estimated value or data derived from the estimated value sothat an indication for the health-related condition of the subject is obtained.
