Is there an alternative to the HealthChanged event?

I'm creating a bit of a "bleeding" script, and i'm looking for the script to fire every time the target takes damage. Currently, the script fires until the target reaches max health. I'm guessing this is something to do with health regen? Here's the block of code, i'm still pretty new to scripting, and if there's any better way out there I would be deeply greatful. Here's the enclosed function:

Definition:

local function damage(severity,lethality)
    script.Parent.Rate = severity
    if humanoid.Health > 0 then
    wait(0.5)
    else
    script.Parent.Rate = 0
    script.Parent.Size = NumberSequence.new(lethality)
    end
end

Called:

humanoid.HealthChanged:Connect(function()
    damage(12,0.1)
end)