Hey guys, are you thinking now may be your T-time? We’re not talking about a round of golf with your weekly foursome. We’re talking about the hugely popular trend of testosterone replacement.

More than 2.3 million prescriptions for T therapy, via gels, pills and injections, were written last year, triple the number just 12 years ago. But that’s not necessarily good news.

When a group of University of Texas docs reviewed the health records of 10 million men who had started testosterone replacement therapy, they found that 25 percent had not had their T levels measured to see if they really need the hormone supplement.

Docs, stop doing that!

Guys, insist on being tested first, and repeatedly. And remember Roizen’s Rules for a Younger You No. 11: If any treatment is going to last more than three days, get a second opinion.

For men with truly low T levels, extra testosterone can be life-changing, boosting energy, firing up a flagging libido and slowing down muscle and bone loss. But even for them, the jury is still out on the long-term effects on a man’s heart and prostate.

And while more and more short-term reports suggest T therapy does not raise your prostate-cancer risk, we agree with researchers who want to see more long-term evidence that it’s safe, since we know male hormones are prostate-cancer cells’ main fuel source.

Also, we don’t have any solid info on the benefits versus risks for guys who aren’t diagnosed with low T, but want to use it because they think it will boost their energy, muscle tone and sexual performance. (We worry the benefits don’t outweigh the risks.) So here’s what to think about before you T it up:

A guy’s testosterone level naturally declines about 1 percent every year after age 30, and that shouldn’t cause problems. It’s true that after age 70, about 30 percent of guys may have clinically low levels (below 300 ng), but most have no symptoms from it.

Low T may not be what’s making you tired, killing your sex drive or making you depressed. Everything from being overweight to having diabetes, high cholesterol and depression could be responsible for a lower sex drive and erectile dysfunction. A lifestyle makeover with powered-up nutrition and daily physical activity may be what you need to jump-start your sex life and save your life. And talk to your doc to see if medications you take may be causing unwanted side effects. You may be able to change your dosage or medication.

Always get a blood test (or two) to check your testosterone level before signing up for T replacement. And do it in the morning. Your testosterone level is highest when you get up and fluctuates during the day. Coffee and alcohol make it go up, as does watching an action movie or your favorite sports team. If they win it really surges; if they lose it plummets!

If your T level is below 300 ng, you may have low T, but to be sure, ask for a second check. And even a level of 300 or less may not be clinically significant (although it’s associated with increased abdominal fat, which is a health risk).

In a new report from Massachusetts General Hospital, doctors found guys didn’t see significant muscle-mass loss or libido problems until their T level fell below 200 ng.

While the Mass General study wasn’t designed to set prescribing levels, we think it calls the 300 ng definition of low T into question and suggests a smarter way to decide whether you need T replacement therapy.

That’ll help you avoid its potential side effects, including acne, fluid retention, breast enlargement, worsening sleep apnea and even shrinking testicles. (Side effects aren’t just your risk; if your children or female partner come in contact with the testosterone supplement, it can cause all kinds of problems.)

Clearly, you should use it only if what it delivers fits your physical needs to a T.

Mehmet Oz, M.D. is host of “The Dr. Oz Show,” and Mike Roizen, M.D. is Chief Wellness Officer and Chair of Wellness Institute at Cleveland Clinic. To live your healthiest, tune into “The Dr. Oz Show” or visit www.sharecare.com.