Hemoglobin a1c level is 8.4--is this safe?

Diabetes uncontrolle: Hba1c below 6 is safe for dm. Above 6 , it shows inadequately controlled dm and you need to get your pcp/endocrinologist follwing you . From your side you need to see are you strict enough in terms of diet, medications -tablets/insulin , exercixe, regular follow up with blood checks at home and lab checks periodically recommended by your doctor of blood sugar in addition to hba1c once in 2-3 months.

Diabetes.: A HgbA1C of 8.4 suggests you have diabetes which is not well controlled, and therefore you are at risk for long-term diabetic complications. It needs to be lowered, ideally below 6.5%