A device for reading and interpreting FSH test strips for the estimation of an ovulation date, comprising: - a camera, configured to obtain colour data of successive FSH test strips; and - a processor, configured to evaluate the colour data obtained by the camera, wherein the processor is configured to determine a concentration value of each successive FSH test strip based on the colour data of the camera and to output a signal, characterized in that if the processor determines that a first FSH downward trend of the FSH test strip values is occurring in the successive FSH test strips, wherein the first downward trend of FSH is determined by taking into account six test strip measurements of six consecutive days; wherein the processor is further configured to determine the slope of the linear regression of the six values and to determine the slope of the linear regression of the first five values and the slope of the linear regression of the last five values within the set of six values, wherein the processor is further configured to compare the three slopes amongst themselves and wherein the processor is configured to determine a significant downward trend, if the three slopes fall within a predetermined range. - a camera, configured to obtain colour data of successive FSH test strips; and - a processor, configured to evaluate the colour data obtained by the camera, wherein the processor is configured to determine a concentration value of each successive FSH test strip based on the colour data of the camera and to output a signal, characterized in that if the processor determines that a first FSH downward trend of the FSH test strip values is occurring in the successive FSH test strips, wherein the first downward trend of FSH is determined by taking into account six test strip measurements of six consecutive days; wherein the processor is further configured to determine the slope of the linear regression of the six values and to determine the slope of the linear regression of the first five values and the slope of the linear regression of the last five values within the set of six values, wherein the processor is further configured to compare the three slopes amongst themselves and wherein the processor is configured to determine a significant downward trend, if the three slopes fall within a predetermined range. wherein the processor is configured to determine a concentration value of each successive FSH test strip based on the colour data of the camera and to output a signal, characterized in that if the processor determines that a first FSH downward trend of the FSH test strip values is occurring in the successive FSH test strips, wherein the first downward trend of FSH is determined by taking into account six test strip measurements of six consecutive days; wherein the processor is further configured to determine the slope of the linear regression of the six values and to determine the slope of the linear regression of the first five values and the slope of the linear regression of the last five values within the set of six values, wherein the processor is further configured to compare the three slopes amongst themselves and wherein the processor is configured to determine a significant downward trend, if the three slopes fall within a predetermined range.