All patients have the right to be intimately involved in their health care. But does that mean you should run your own medical tests or even self-diagnose a condition?

An increasing number of Americans are saying yes, using one of the many do-it-yourself screening kits now on the market to test their blood or urine for a slew of ailments. And many others are testing themselves daily with their doctor’s approval — monitoring, for example, their blood glucose or blood pressure.

Consumer Reports reviewed the literature and consulted experts to determine when, if ever, consumers should consider some of the most popular home-test kits. Note that you shouldn’t embark on any home testing, even the kinds Consumer Reports recommends, without a consultation with and approval from your doctor.

Tests that monitor disease
Blood glucose

Worth doing? Yes.

For whom? People with Type 1 diabetes. For Type 2 diabetes, the benefit is less clear; check with your doctor. Monitoring glucose is essential for managing Type 1 diabetes and is nearly always encouraged by doctors who treat that condition.

Glucose readings can help patients adjust their diet and exercise routine, and tailor insulin doses to keep their levels in the proper range. In Consumer Reports’ 2011 tests of home blood glucose meters, the Accu-Chek Compact Plus ($20) scored highest overall.

Prothrombin (blood-clotting factor)

Worth doing? Yes.

For whom? Certain people who take blood-thinning drugs such as warfarin (Coumadin and its generic cousins).

Warfarin and other blood thinners can be lifesaving for people with atrial fibrillation or disorders that can cause blood clots in the brain, heart, legs or lungs. But the medication can also cause dangerous, uncontrolled bleeding that can be fatal in some cases. Self-monitoring can greatly reduce that risk.

Blood pressure

Worth doing? Yes.

For whom? People with elevated or borderline-elevated blood pressure.

Careful monitoring of blood pressure over time is key to treating hypertension, and research shows that an average of several readings over the course of a week provides a more reliable measurement than a sporadic reading. A home monitor not only is helpful for meeting the recommended number of readings but also can be more accurate than the testing done at a doctor’s office, where blood pressure can be elevated by patient anxiety (known as “white-coat hypertension”). Top-ranked models from Consumer Reports’ latest tests included the Omron 10 Series BP785 arm monitor ($80) and the Omron 7 Series BP652 wrist monitor ($60).

Cholesterol

Worth doing? No.

Since people with diabetes and hypertension can benefit from home monitoring, you might think that tracking your cholesterol at home would be a good idea, too. But Consumer Reports’ experts say you should skip them. Unlike blood glucose and blood pressure, HDL (good) and LDL (bad) cholesterol levels don’t change much from day to day, and thus don’t require frequent adjustments of drug dosages.

Diagnostic tests

While the tests in the preceding section are used to track ongoing conditions, the ones in this group are meant to help you screen for a given condition. While the market teems with options, the Food and Drug Administration has okayed only a handful, including the ones covered below. Note that any at-home diagnostic screening should almost always be coupled with a medical exam.

Fecal occult blood

Worth doing? Yes.

For whom? Annually between routine colonscopies for people 50 and older (45 and older for African Americans; age 40 for people with a family history of colon cancer or polyps).

Fecal occult blood — blood in your feces that you can’t see in your stool or on toilet paper — can be an early sign of a gastrointestinal condition such as Crohn’s disease, abnormal growths (polyps) or colon cancer. Make sure you follow the directions closely, including avoiding red meat and certain medication, such as aspirin and ibuprofen, for several days before testing.

Tests for a yeast infection or urinary-tract infection

Worth doing? Yeast infection: sometimes. UTI: probably not.

For whom? Women with nonrecurrent infections.

The vaginal test for yeast infection measures pH, which can detect an infection but can’t necessarily tell what kind it is. It allows women who suspect a yeast infection to help confirm it and treat themselves with over-the-counter antifungal drugs. While home tests for urinary-tract infections may be accurate, the results are helpful only if your provider is willing to call in a prescription for antibiotics without seeing you, which many aren’t. So if you can’t see your doctor, it might make more sense to go to an urgent-care or walk-in clinic where you can get both a diagnosis and, if needed, a prescription.

Copyright 2012. Consumers Union of United States Inc.