Bruises on the arms
Bruising around the arms can easily occur for several causes, but in your particular case, diabetes is an unlikely cause. Bruising and diabetes join hands, so to speak, in a condition known as acanthosis nigricans, which manifests as brown or black patches of skin discoloration in folds and creases of the body, especially in the axes and the neck.
It occurs when insulin, usually associated with type II diabetes, spills over through the skin as a result of insulin resistance. These other symptoms can always be evaluated to rule out diabetes: increased thirst, more frequent urination, fatigue, extreme hunger, blurred vision, weight loss, and recurrent infections.
Unlike nigricans with acanthosis, bruises occur when an injury or trauma causes internal bleeding in the skin. Common suspects for unexplained bruising in the arms are:
- Thorough exercise, e.g., track, field and weightlifting, often causing blood vessel breakage
- Vitamin C, B12, K and folic acid deficiency
- Medications and supplements and their side effects. Aspirin, warfarin, corticosteroids (for example, prednisone), anti-inflammatory drugs (ibuprofen), and dietary supplements including fish oil, ginger, garlic, and ginkgo can cause unexplained bruising.
- A bleeding or blood clotting disorder, e.g. leukemia
- Hepatitis, e.g., primary biliary cirrhosis
- Blood-vessel inflammation