NPC Damage script not playing animation or other things?

I've been going at this for around an hour now, and can't get my head around why it won't work. It's a damage script where if the NPC is below 65 health, it plays a hurt animation, as well as shows blood and changes face. However, when I change

if script.Parent.Health <= 65 then

to

if script.Parent.Health >= 65 then

it works perfectly but does above 65 health, but when I change it to <, symbolizing below, the script simply does not function. If you have a fix, PLEASE help me.

local humanoid = script.Parent
local cHealth = humanoid.Health
local animation = script.Parent.Parent.LowHealth
local LA = Instance.new("Animation")
LA.AnimationId = "rbxassetid://5540835623"
local LowHealth = humanoid:LoadAnimation(LA)

if script.Parent.Health <= 65 then
	LowHealth:Play()
	script.Injured.Parent = script.Parent.Parent.Head
	script.Parent.Parent.Head.Normal:Destroy()
	script.Parent.Parent.Head.Blood.Enabled = true
	script.Parent.Parent.Head.Blood2.Enabled = true
	script.Parent.Parent.Head.Blood3.Enabled = true
	wait(2)
	script.Parent.Parent.Head.Blood.Enabled = false
	script.Parent.Parent.Head.Blood2.Enabled = false
	script.Parent.Parent.Head.Blood3.Enabled = false
-----------------------------------------------------------------------------
elseif script.Parent.Health <= 45 then
	LowHealth:Play()
	script.Injured.Parent = script.Parent.Parent.Head
	script.Parent.Parent.Head.Normal:Destroy()
end

You have to place that code in a loop, so your code runs more than one time

local humanoid = script.Parent
local cHealth = humanoid.Health
local animation = script.Parent.Parent.LowHealth
local LA = Instance.new("Animation")
LA.AnimationId = "rbxassetid://5540835623"
local LowHealth = humanoid:LoadAnimation(LA)

while true do -- The loop will make the code run infinitly
    if script.Parent.Health <= 65 then
        LowHealth:Play()
        script.Injured.Parent = script.Parent.Parent.Head
        script.Parent.Parent.Head.Normal:Destroy()
        script.Parent.Parent.Head.Blood.Enabled = true
        script.Parent.Parent.Head.Blood2.Enabled = true
        script.Parent.Parent.Head.Blood3.Enabled = true
        wait(2)
        script.Parent.Parent.Head.Blood.Enabled = false
        script.Parent.Parent.Head.Blood2.Enabled = false
        script.Parent.Parent.Head.Blood3.Enabled = false
-----------------------------------------------------------------------------
    elseif script.Parent.Health <= 45 then
        LowHealth:Play()
        script.Injured.Parent = script.Parent.Parent.Head
        script.Parent.Parent.Head.Normal:Destroy()
    end
    wait(1) --Don't forget to add waits on all loops
end