Dear Max:

I understand what you are going through. I struggle with diabetes myself. My diet is not what one would call a diabetic diet, but as long as my numbers are less than 180 or so I do not worry about it. The standard of like 75-110 is way too low a standard according to every nurse I have talked to.

In my case, diabetic pills and diet did not work. Thus, I was placed on insulin. I take a long-acting insulin twice a day, and a short-acting insulin before meals. With this regime my numbers came down. In fact, now I have an occasional problem of my sugars being to low.

You may want to talk to your doctor about insulin treatment if the pills are not working for you. UNDER NO CIRCUMSTANCES should you avoid going to the doctor. If you avoid the doctor has is he to know that your current treatment plan is not working?

As for mortal sin, in order for a sin to be mortal three conditions must exist. If any one of the following conditions are lacking then the sin does not rise to the level of mortal sin:

1) the sin must be grave
2) one must know that the sin is grave
3) one must have a completely unimpaired volition to commit the sin anyway with conscious deliberation.

On the 3rd condition, anything that impairs one's free will, one's ability to make a truly free choice, then a state of diminished capacity exists which can reduce or even eliminate culpability for the sin. In criminal law an example of this is "found innocent by reason of insanity." This concept in criminal law came from Catholic theology. 

Those who wish to kill themselves, for example, are considered in a state of diminished capacity and thus the sin of suicide, which is grave, is not imputed to them as mortal. This is because we know that is nearly all cases of suicide there is a psychological impediment to making a truly free choice.

The Catechism speaks about health:

Respect for health

2288 Life and physical health are precious gifts entrusted to us by God. We must take reasonable care of them, taking into account the needs of others and the common good...

2289 If morality requires respect for the life of the body, it does not make it an absolute value. It rejects a neo-pagan notion that tends to promote the cult of the body, to sacrifice everything for its sake, to idolize physical perfection and success at sports. By its selective preference of the strong over the weak, such a conception can lead to the perversion of human relationships.

There is no mention that lack of attention to good health is a grave sin. When a sin is grave the Church specifically says so.

We must remember that St. Thomas Aquinas was a very fat man. It is said that he was so fat that he cut a semi-circle into his supper table so he could sit closer to the table. This very fat man was not only made a saint, but a doctor of the Church, and the greatest of the saints in our history.

In any event, I suspect a diminished capacity in your case anyway. You say, "I lack the necessary discipline to stay away from sugar and carbohydrates". This implies a psychological issue that impairs your ability to discipline yourself. I suggests that you seek out a mental health professional to explore why you lack discipline. The combination of medical and psychological treatment may help you a lot.

But, do not beat-up yourself. Do the best you can, with perhaps the help of a counselor. Always make your appointments and be honest with the doctors. There is no mortal sin here that I can see from what you have told me.

God Bless,
Bro. Ignatius Mary