Python function to calculate blood levels of medication

gistfile1.txt

# dose: daily dose
# halflife: half-life in hours
# start_level: initial blood levels
# days: days to model
def blood_level(dose, halflife, start_level=0, days=200):
    # starting level = 0
    level_0 = start_level
    # level after first dose = dose
    level = dose + start_level
    
    # hf in days
    hf_days = halflife / 24
    
    # start at day 0
    day = 0
    levels = [level_0]
    # loop through days
    while day < days:
        # how much will the levels decrease today
        day_decrease = (level / 2) / hf_days
        
        # subtract the decrease
        level -= day_decrease
        
        # add the daily dose
        level += dose
        levels.append(level)
        # increase the day
        day += 1
        
        print("Day:", day, "starting level:", level_0, "end level:", level)
        level_0 = level
        
    plt.plot(np.arange(days+1), levels)
    plt.xlabel("Days")
    plt.ylabel("Blood Level")
    plt.show()