They may cover you, but there will be big exclusions.

They will definitely exclude diabetes itself, and all degenerative diseases
associated with it - vascular (cardiovascular, hypertension, cerebrovascular
- strokes, peripheral vascular system), optical (eyes - retinopathy, glaucoma, cataracts),
renal (kidneys, renal hypertension).

(Bear in mind that diabetes compromises the entire body.)

In effect, a bit chunk of your health will not be covered. Once I told a
friend about Tokyomarine's Medic Plus., a top-up (excess RM 10,000) policy.
They sent a Bengali senior underwriting staff to assess him, found out his
HbA1c was high, and offered him a policy with so many exclusions that it
was virtually useless.

Needless to say, he never bought it, and neither would I.

Any agent know who to contact for this?

so any update? which insurance cover for diabetes T1?