There is no published threshold, and carriers set their own bands. What is consistent is that they read the total-to-HDL ratio rather than a single total figure, so no one number answers the question.
This gets asked constantly and it does not have the answer people want, for a structural reason.
Why no number exists
No carrier publishes the underwriting manual that sets its cholesterol bands, and the bands differ between carriers. Any specific figure quoted online is broker-reported at best. The constraint is the same one that applies across impaired-risk underwriting and is explained on how underwriting works.
What replaces the number
The ratio, as above. Carriers also apply an upper bound on total cholesterol independently of the ratio, and an unusually low total can itself prompt questions, because it occasionally indicates an underlying problem rather than good health.
The more useful question
Not “is my number too high” but “what is my ratio, and is it trending”. Divide your total by your HDL and you will know more about how an application will go than any threshold chart could tell you.
If the reading is unrepresentative
Cholesterol moves. If your most recent panel followed a bad few months and you have a documented history of better numbers, supply the history rather than the latest result alone — and if a repeat panel is due soon, it is often worth waiting for it rather than applying on your worst reading.
The full treatment of this topic is on High cholesterol.