Now that the breadboard prototype appears to be working, it's time to make a more permanent (and smaller) version. With a few minutes of googling, I found a website called EasyEDA, that allows you to design PCBs using their online tool. It was fairly intuitive to learn and, even better, it included a massive user library of part dimensions, and an automatic conductor router (in other words, it generated the hard part for me).

When considering the design, I wanted it to be small and concise. To that end, I made a few adjustments to Bindhammer's schematic. Here is my modified version.

The primaries differences are the quad switch is gone and with it the op-amp integrator between pins 13 and 14 it controlled. The function of an op-amp integrator is to output a voltage proportional to the integral of the input. In a glucose meter, the graph it produces is in some circumstances more linear than the the direct op-amp output.

In my tests, it was not, so I took it out, along with the physically largest chip. This is the graph it made. X-axis is time, Y-axis is ADC voltage.

Top: integrator active; Bottom: no integrator

One other notable change is that capacitor 6 and 7 are no longer polarized. I believe these capacitors are to filter out AC voltage and noise, and I think they can do that when they're not polarized. I am certain, however, that non polarized capacitors are much, much smaller.

With the new design, I confidently connected up some virtual wires and told the auto router to route me some conductors.

Here is the virtual estimation of the result. Here is the gerber file.

EasyEDA also offers milling, and since I got it down to about one square inch, it only cost $10 for 5 boards! I went ahead and got 10 cause 5 was the minimum and 10 was the same price as 5. I also ordered another set of resistors and capacitors (checking to make sure they were surface mount) from Mouser.