The answer to your question depends on a number of factors. If the leave is protected under the FMLA/CFRA or possibly the ADA/FEHA then the employer may be required to grant you intermittent leave. If the employer’s policy only allows sick leave in minimum increments of 4 hours then the employer may, or may not, be able to apply its policies. Both the ADA and the FEHA require employers to make modifications to their policies in order to accommodate the known disabilities of its employees.

If the sick leave is not for a disability and is not otherwise covered by the FMLA/CFRA then the employer may be able to require you to use sick leave in specific blocks of time. You, then, can decide whether to take sick leave in the allotted block of time or just suffer a loss of an hour’s pay for the time off.