When it comes to pre existing conditions, insurers will be looking to see whether the condition is likely to increase the risk of you claiming on the policy.
As a Life Insurance policy pays out on death, any pre-existing condition that is life threatening, or that reduce life expectancy, will likely have an impact on the premium or terms of the policy.
For anything pre-existing which isn’t life threatening and isn’t likely to affect lifespan it would be more likely that standard terms can be obtained.
With serious pre-existing conditions insurers will typically consider the following: type of condition, when the condition was diagnosed, any medication/treatment, any relevant associated factors such as smoker status and height/weight.