Fasting insulin bloodwork doesn't always indicate Insulin Resistance even if you have other symptoms. This article talks about the difficulty in diagnosing IR and that it should be diagnosed by observation of physical symptoms and family medical history.
http://www.aafp.org/afp/20010315/1159.html
Here are a list of physical symptoms of IR. You don't have to have all of them to be IR.
Constant tiredness, or feeling like you've been hit by a truck, even after a good night's sleep. Feeling exhausted when you wake after a full nights sleep or having to nap during the day to get thru the day.
Acanthosis Nigricans - Dark patches usually found in the creases under your arms, on the back of your neck and at your groin. You may also see a darkening of skin under your breasts, at the waist, knees and elbows.
Skin tags
Hypoglycemia - getting shaky, dizzy, tired, confused when you go too long without eating or one or two hours after eating
Feeling hungry all the time
Central obesity - aka belly fat or being apple shaped often with thin arms and legs
Oily skin & hair
Acne
High testosterone - which causes male pattern baldness (hair loss at temples and top of head) or overall thinning hair. It also causes hirsutism (hair where girls don't want it).
Thin lips - I've only read this symptom in one place, but it was certainly true of me. Once I started Met they returned to a plumper size. It might be related to the high testosterone.
A feeling like "brain fog"...being unable to concentrate or being forgetful
Feeling of food lying in your stomach for hours
Slow or no weight loss after religiously dieting and exercise
Polycystic ovaries
High blood lipids (cholesterol, triglycerides)
High cortisol
High blood pressure
Irregular periods (too few, too many, unpredictable, etc.)
Who has the highest risk for being IR?
People with a family history of diabetes, who experienced gestational diabetes, had large babies or have American Indian ancestry (another source includes Mediterranian ancestry). Also, the more overweight you are, the worse your IR is likely be. Everybody gets more IR as they age.