Slowly fade blood onto the players screen as they take damage?

I am trying to make a script that will slowly fade blood onto the players screen. The amount of blood shown will slowly increase the lower their health gets.

I started to attempt this myself, but the way I am doing it seems inefficient. Is there a better way other than manually stating the health values?

local Player = game:GetService("Players").LocalPlayer
local Character = Player.Character or Player.CharacterAdded:Wait()

local PlayerUI = Player:WaitForChild("PlayerGui")
local BloodEffect = PlayerUI:WaitForChild("ScreenEffects"):WaitForChild("Blood")

Character.Humanoid.HealthChanged:Connect(function(NewHealth)
    if NewHealth >= 80 and NewHealth <= 99 then
        for i = 0,.9,.05 do
            BloodEffect.ImageTransparency = i
            wait()
        end
    else if NewHealth >= 60 and NewHealth <= 79 then
            for i = 0,.7,.05 do
                BloodEffect.ImageTransparency = i
                wait()
            end
        end
    end 
end)