Men spill it, seal friendships with it, and, if they’re aging rock guitarists, have it purified at Swiss clinics. But blood also tells a detective story. Just as the amount, color, odor, and feel of the oil on a car’s dipstick offer clues about wear and tear on the engine, your blood can reveal critical details about the running condition of your entire body.

Of course, first you need to know what to look for and how to interpret the findings. That’s why we’ve created a guide on how to read the red stuff. Order up all six of these tests at your next physical and you’ll be doing more than just kicking the tires.

  1. Start with the Basics: The CBC

This is one of the most commonly ordered blood tests, which is the measure of the concentration of white blood cells, red blood cells, and platelets in the blood. The size of your red cells can be a good indicator of nutritional deficiencies. You want this number, called the mean corpuscular volume, or MCV, to be between 85 and 95 fl. You also want to see that your red cells come in all different sizes, which shows cells at different stages in their life span.

  1. Learn Your Sugar Score

Blood tests are like radar for tracking type-2 diabetes. The standard measure is the fasting glucose test, which is part of what sounds like a congressional subcommittee: the Comprehensive Metabolic Panel. Fasting glucose is a one-off reading, so it’s often paired with the A1c test of your average blood-glucose level over the preceding 2 to 3 months.

But if you score high on either of these tests—above 100 milligrams per deciliter (mg/dl) on the fasting test, or above 6 percent on the A1c—you should demand an oral glucose-tolerance test (OGTT).

Take an OGTT regardless of your fasting-glucose and A1c scores if you score 140 mg/dl or higher on a random glucose test (one you take without fasting beforehand), your belly’s bulging (that is, your body mass index is 30 or higher), or you experience head-snapping slumps after a high-carbohydrate meal. Ditto if you have a family history of diabetes or heart disease. The test can last 2 to 5 hours, depending on the version you take. If you hit the 2-hour mark of an OGTT with a reading above 140 mg/dl, you’re prediabetic. If it’s above 200 at that point, there’s no “pre” about it.

  1. Keep an Eye on Fats, Too

If you have risk factors for cardiovascular disease—such as past cardiac events, a family history of the disease, hypertension, or you’re a smoker—your target LDL may be below 100 mg/dl. If you’re at high risk, ask your physician about an expanded lipid profile test, like the Vertical Auto Profile, which further breaks down the dangerous subtypes of LDL.

  1. Look for Signs of Inflammation

The process by which inflamed arteries lead to cardiovascular disease is invisible except for a tracer—an elevated level of C-reactive protein (CRP) in your blood.

“If your CRP as well as your total cholesterol is high, you’re at an even greater risk of having a heart attack than you would be with either risk factor by itself,” says David Sandmire, M.D., a professor of physiology at the University of New England in Biddeford, Maine.

Make sure you feel perfectly healthy the day of your appointment: This highly sensitive test picks up all sorts of inflammation, even from a paper cut.

That’s a good reason to take it twice, at least a month apart, and average the two scores. Yours should fall under 1 milligram per liter; if it’s above 3, your heart-attack risk doubles.

If your score is too high: Smokers, take note: “It’s almost certain that CRP levels will decrease after you quit,” says David W. Johnson, Ph.D., an associate professor in the college of osteopathic medicine at the University of New England and coauthor of Medical Tests That Can Save Your Life.

If your lungs are already a smoke-free zone, raise a glass. A Spanish study found that red wine reduced inflammation markers by 21 percent.

  1. Have Your Prostate Checked

Pay great attention to tracking your prostate-specific antigen (PSA). Elevation of this marker can signal a problem—at least sometimes. PSA testing is not an exact science, because factors external to the prostate can cause the marker to rise. A high PSA reading may point to a benign enlargement of the prostate or even a bacterial infection known as prostatitis.

That’s why the trend can be as important as the static number. Have a PSA test done every year and compare the result with that of the year before, to see if further investigation is warranted.

  1. Don’t Forget Your Thyroid

Thyroid problems hit men as well as women, and stress and poor sleep are often the culprits. “Many people don’t sleep as well as they should, so the body overcompensates,” says Dr. Berkowitz.

With an overactive thyroid, there may be signs of a goiter—a swollen area in the neck. Hyperthyroidism, as it’s called, can also lead to an increased heart rate, anxiety, sleep problems, and weight loss.

Symptoms of an underactive thyroid (hypothyroidism) may include personality changes, hair loss, weight gain, and a cloudy memory.

Both thyroid conditions can lead to more serious, life-threatening illnesses when left untreated. The thyroid-stimulating hormone (TSH) test will determine if you have a problem.

If your results are off the mark: Your doctor may order the more specific free T3 and free T4 follow-up tests.