Millions of consumers are using the Internet to get health information. And thousands of web sites are offering health information. Some of those sites are reliable and up-to-date; some are not. How can you tell the good from the bad?

Some websites that sell medicine can be not state-licensed pharmacies or aren't pharmacies at all; or may give a diagnosis that is not correct and sell medicine that is not right for you or your condition; or won't protect your personal information.

You have to talk with your doctor and have a physical exam before you get any new medicine for the first time. Use only medicine that has been prescribed by your doctor or another trusted professional.

Be sure your privacy is protected: look for privacy and security policies that are easy-to-find and easy-to-understand. Don't give any personal information such as social security number, credit card, or medical or health history, unless you are sure the website will keep your information safe and private.

Reading the label every time you use a nonprescription or prescription drug and taking the time to learn about drug interactions may be critical to your health. You can reduce the risk of potentially harmful drug interactions and side effects with a little bit of knowledge and common sense.

Early in a drug's development, companies conduct research to detect or predict potential interactions between drugs. Experts evaluate the drug-interaction studies as part of assessing a drug's safety.

Mixing two drugs together could make one of the drugs ineffective. The combination also could increase a drug's effect, and be harmful. The result might be mild symptoms such as nausea, stomach upset, or headache, or more serious symptoms such as a dramatic drop in blood pressure, irregular heart beat, or damage to the liver-the primary way that drugs pass through the human body.

When a drug is taken orally, it usually travels from the stomach to the liver, where it can be metabolized-the process of breaking down and removing chemicals from the body. Enzymes are complex proteins that act as catalysts in starting or speeding up chemical reactions. They cause a specific chemical change in other substances without being changed themselves.

It used to be that the only way to test for drug interactions was in people. Now drug companies can take five test tubes with the five major pathways for metabolism and put their drugs in to see whether it's metabolized by CYP450. This allows to generate a list of possible interactions based on their findings.

Not everything that happens in a test tube will become meaningful in humans, though. Results from these test-tube studies can tell us whether need to do further testing in people to find out if an interaction is clinically significant.

Health professionals also use computer systems with drug-interaction screening software, electronic prescribing, and other technology. Mark Langdorf, M.D., chair of the department of emergency medicine at the University of California, Irvine, says, "In a busy emergency room, you have to quickly find out what a patient is taking and how those drugs could interact with other treatments."

So rather than asking patients what medications they take, doctors should make the questions specific: "Are you taking any over-the-counter medication? Are you taking any herbal treatments or vitamins?"

But it is good way -- consumers remind doctors of everything they take when they are prescribed a new medication. So a patient might say: "Now remember, I'm also taking birth control pills. Is there a risk of interaction with this new medicine?"

Drug interactions with other drugs includes both prescription and over-the-counter medicines. Tricyclic antidepressants such as Elavil (amitriptyline) and Pamelor (nortriptyline) can interfere with blood pressure-lowering Catapres (clonidine). Taking the antibiotic Cipro (ciprofloxacin) with antacids lowers Cipro's effectiveness.

Drug interactions with dietary supplements includes herbs and vitamins, which can interact with drug-metabolizing enzymes. St. John's wort is an herb commonly used by people with cancer to improve mood, but research has shown it interferes with the metabolism of irinotecan, a standard chemotherapy treatment. Vitamin K (in dietary supplements or food) produces blood-clotting substances that may reduce the effectiveness of blood-thinning medicines like warfarin.

Drug interactions with food and beverages, for example, taking quinolone antibiotics such as ciprofloxacin with food and drinks such as colas, coffee, and chocolate that contain caffeine may cause excitability and nervousness. There can be a potentially fatal increase in blood pressure if food containing tyramine is eaten when taking monoamine oxidase inhibitors, drugs that treat mood disorders.

Examples of food with tyramine are cheese and soy sauce. Grapefruit juice should not be taken with certain blood pressure-lowering drugs or cyclosporine for the prevention of organ transplant rejection. Alcohol should not be taken with pain relievers such as Tylenol (acetaminophen) or ibuprofen because of the increased risk of liver damage or stomach bleeding.

Before using any medicine--as with many things that you do every day--you should think through the benefits and the risks in order to make the best choice for you.

For example, every time you get into a car, there are risks---the possibility that unwanted or unexpected things could happen. You could have an accident, causing costly damage to your car, or injury to yourself or a loved one. But there are also benefits to riding in a car: you can travel farther and faster than walking, bring home more groceries from the store, and travel in cold or wet weather in greater comfort.

To obtain the benefits of riding in a car, you think through the risks. You consider the condition of your car and the road, for instance, before deciding to make that trip to the store.

The same is true before using any medicine. Every choice to take a medicine involves thinking through the helpful effects as well as the possible unwanted effects.

For example, if facing a life-threatening illness, you might choose to accept more risk in the hope of getting the benefits of a cure or living a longer life. On the other hand, if you are facing a minor illness, you might decide that you want to take very little risk.

To lower the risks and obtain the full benefits of medicines you need a)talk with your doctor, pharmacist, or other health care professionals; b)know your medicines--prescription and over-the-counter; c)read the label and follow directions; d)avoid interactions; e)monitor your medicines' effects--and the effects of other products that you use

You need keep an up-to-date, written list of ALL of the medicines (prescription and over-the-counter) and dietary supplements, including vitamins and herbals, that you use--even those you only use occasionally.

You have to always tell your doctor if you are or might become pregnant, or if you are nursing a baby. Always ask questions about any concerns or thoughts that you may have.

Before use a medicine make sure you understand the directions; ask your doctor if you have questions or concerns. Always double check that you have the right medicine.

Before starting any new medicine or dietary supplement (including vitamins or herbal supplements), ask your doctor again if there are possible interactions with what you are currently using.

You have to know what to do if you experience side effects and when to notify your doctor, and know when you should notice an improvement and when to report back.

Look around, touch life!