How to troubleshoot a boost converter (ADP1613)?
So, the input voltage is 5V and you're trying to get 5V output?  

If that is the case, a boost isn't going to work out for you. A boost can only output a higher (or equal) voltage than the input. In fact it can't supply anything less than the input voltage (minus the diode drop), since current from the input will pass through L1 and D1 to Vout. This is true always. If the switch is switched at some duty cycle, then higher voltage will show up on the output.  If Vin ranges both higher and lower than Vout, you will have to use a buck-boost or sepic converter.

You are correct that with no (or very light load) a very high voltage can show up on the output. Look at the circuit from pin 5 of the AD1613 to Vout. There is just a diode and a capacitor. A peak detector. So, without load, even a whisper thin PWM to the switch will put energy into the inductor that will transfer to Cout with nowhere to go until a leakage path is found. This is why it is common to put a zener diode, rated a little higher than  Vout, across Cout.