Theranos shut down a week ago -- defaulting on a $65 million loan it received from Fortress Investment Group, according to the Wall Street Journal.

As an investor, I see Theranos as an exceptionally compelling story of how a con artist was able to talk many (mostly) wealthy old men out of $1 billion of their money while failing for 15 years to produce any real results.

Many rich people invested at least $100 million in Theranos. These now-poorer rich people include the Waltons, heirs to Walmart founder Sam Walton; Atlanta's Cox family; the family of Secretary of Education Betsy DeVos; and Rupert Murdoch, executive chairman of 21st Century Fox and of News Corp. Their investments in Theranos are now worthless, according to the Journal.

Their loss could be your gain if you do the things they did not do before you invest in a company. And these lessons won't just help you as an investor -- you should heed them if you are thinking about going to work for a startup.

The reason is that startups usually give employees stock options -- in which case you would also be an investor. But perhaps more important than avoiding the financial risk of getting paid in stock options that are likely to be worthless, is the damage to your professional reputation of having worked for a company like Theranos.

Indeed in June when I spoke with a psychiatrist who has known Holmes since she was a child, he sympathized with former Theranos employees who are trying to find new jobs -- a fate he likened to that of former Enron employees.

Here are six things you should do to keep from being Theranosed.

1. Talk to customers and partners to verify the company's claims.

Theranos made bold claims about all the organizations it had partnered with. Indeed when I called one of the ones that was mentioned in a glowing 2014 New Yorker article about Theranos, Pfizer told me it had no deal with the company. If investors had done that -- and talked with other partners, they would have been suspicious.

In general, you should contact customers and partners to verify a company's claims before investing or going to work there.

2. Don't invest unless you review audited financial statements.

I spoke with people who had obtained stock options in Theranos and asked them whether they had ever seen any financial statements. They said they had not. When I invest in companies, I expect to see audited financial statements. If they don't exist, it is a huge red flag.

3. Talk to other investors with more experience to find out what due diligence they did before investing.

When Elizabeth Holmes was trying to convince people to invest in Theranos, it probably did not hurt that she had attracted early investors such as Oracle founder Larry Ellison and Silicon Valley venture capitalists Tim Draper.

Those $100 million investors should have asked them what sort of due diligence they did before investing. I don't know if they asked Ellison and Draper -- but it looks like nobody did due diligence before writing big checks. 

You need to ask other investors how they decided to invest -- and if the answers are not persuasive, run away.

4. Talk to previous employers and colleagues of the CEO before investing.

Before investing in a company, ask previous employers and colleagues what they think of the person. Contact people who have worked with them via LinkedIn -- dig until you get a realistic assessment of the person.

Holmes, a college dropout did not have a long employment history that could have been checked. But most CEOs do.

5. Talk to the CEO's former professors and/or prior investors.

If you are going to invest in a company, find out where the CEO went to school and talk to professors who teach in the department in which the CEO majored. A Theranos investor might have made the mistake of checking with Channing Robertson who headed Stanford's Chemical Engineering Department. He was dazzled by Holmes and served on the board.. 

Before investing -- find out the straight scoop from the CEO's former professors and investors -- not just one fan.

6. Verify the claims on the resumes of top executives.

While it might not have helped much to check on the details of the resumes of Holmes or that of Sunny Balwani, Theranos's former president, it is always a good idea to verify the truth of what top executives claim on their resume before investing -- as former Yahoo CEO Scott Thompson did. If they will lie on their resume, you should not trust them with your money or your reputation.

Before joining a company, check these six things. If that's too much trouble, you could be endangering your net worth and reputation.