How can I spot fake pills?
The best test you can do at home is to heat a small glassful of water to bath temperature (100F/37C) and see if one of the pills dissolves completely in the water. This works because bath temperature is roughly human body temperature and all pills should dissolve in water at human body temperature, however counterfeiters sometimes use talc, dolomite, anhydrite, or gypsum to bind the pill together, and these substances do not dissolve well.
Another test you can do at home is to drop part of the pill in vinegar. If the pills fizzes then that increases the likelihood that it is a fake. This is because the fizzing suggests it contains calcium carbonate as a 'filler'. Although it is used in genuine medicines as well sometimes as a harmless material to bulk out the pill, calcium carbonate is more often used in fakes because it is cheaper than starch (which is the filler ingredient more often used in genuine medicines).
If you have access to a highly sensitive set of scales you could try comparing the weights of different pills in the batch that you have received. If the pills all weigh the same (to within 1%) then that is a good sign; the weight of pills in batches of fake medicines often varies, by as much as 10%.
Use the free pill identifier tool on the drugs.com website: Pill Identification Wizard from Drugs.com
Type in the shape and color or the imprint code found on the capsules or pills. This is quite an imperfect way to check if the pills are real, because obviously it is easy for forgers to put the correct imprint code on fake medicines, but it will at least help to identify the crudest fakes.
In a laboratory setting a variety of techniques can be used to determine the composition of a pill: various types of 'wet chemistry' techniques; thin-layer chromatography; X-ray fluorescence; high-performance liquid chromatography, and mass spectrometry. But these tests require expensive equipment to perform, and can be time-consuming to analyze.
How much of a problem is this when buying medicines online?
“The best 'guesstimate' is that 1% of drugs in the developed world are counterfeit. In developing nations, between 10 and 50% of drugs are thought to be fake.” (Source: Chemical and Engineering News, January 4, 2010 Volume 88, Number 1, pages 27-29 Fake Pharmaceuticals | Science & Technology | Chemical & Engineering News)
A lot of medicines bought online are manufactured in developing countries. Also some online pharmacies use "drop shippers" (wholesale companies that also take care of posting the medicines to customers on behalf of the pharmacies) so they don't have much control over the quality of the medicines that they send out, and cannot check easily if the drop shipping company they employ has been buying poor quality medicines from China, for example. For these reasons it pays to be careful in selecting an online pharmacy to order from, and using pharmacyreviewer.com to communicate with others to check which pharmacies are consistently reliable.
A point worth keeping in mind is this: just because the medicine is fake it does not mean that it does not contain the active ingredients which it should. It just means it was not manufactured by the company it says on the box. There is a lot of hype put about by the marketing departments of the big pharmaceutical companies instilling fear in people that if they buy medicines online they will end up with rat poison, but instances of counterfeit medicines actually containing harmful substances are pretty rare (why would anyone in the business of manufacturing counterfeit medicines put poison in them?) Much much more common is that they will contain either too much or too little of the active ingredient, and the rest of the pill will be made up of filler substances such as calcite or aspirin. From the limited statistics available it appears that buying medicines online, even when the medicines are manufactured in developing countries, is generally pretty safe.
Moreover, most of the highest rated online pharmacies on pharmacyreviewer.com sell medicines either made by the big pharmaceutical companies, or by large, long-established “generics”manufacturers, such as Dr Reddy's in India, which have quality control procedures in place comparable to the big pharmaceutical companies (indeed, Dr Reddy's for example has a manufacturing agreement with Glaxo Smithkline Inc, in which some Glaxo Smithkline medicines are manufactured in Dr Reddy's factories.)