<i>Is there a practical guide to inexpensive home testing?</i><p>None that I know, might exist though. I mean, you can buy dead cheap properly working test kits for MDMA for instance, then why not for B12 you&#x27;d wonder.<p>But rather than testing the B12 itself you might just (or also) test if you have enough of it. Many vegans I know make a yearly appointment with their doctor for a blood test looking for defficiencies in a number of substances. Most are always fine btw. Oh and google came up with this: <a href="http:&#x2F;&#x2F;www.testcountry.com&#x2F;products.html?product=1883" rel="nofollow">http:&#x2F;&#x2F;www.testcountry.com&#x2F;products.html?product=1883</a>. Again, hard to tell if it&#x27;s ok - but you could compare it with blood test results. Then again, blood test might be cheaper than this kit.