A home sperm test is set to join dozens of female fertility predictors on drug store shelves this spring.

Walgreen's and CVS are already selling the sperm-counting kit, called  SpermCheck Fertility, online. Now they're banking on men - and their mates - favoring a quick pick-up at the drug store over a trip to the urologist.

"There is nothing like it on the shelf," Maeve Egner of Fusion Marketing, the company hired to help market SpermCheck,  told Bloomberg. "It's plugging a gap."

The $40 test is set to hit stores in April. To use it, a man mixes his semen with a solution in the kit and drops it onto a test strip. A reddish line means the sperm count is above 20 million per milliliter, which is considered normal. A negative test shows no color and means the man should "should consult a physician about a complete fertility evaluation," according to the kit's instructions.

Studies have found that SpermCheck Fertility correctly counted sperm 96 percent of the time compared with laboratory sperm- counting methods. But some doctors say sperm count is only one aspect of male fertility.

"There are four major things we look for," said Dr. James Goldfarb, a fertility specialist at UH Case Medical Center in Cleveland: The number of sperm; their shape; their mobility; and the volume of the ejaculate. "This test only measures one thing."

While a low sperm count may signal a problem, Goldfarb said a count of 15 million per milliliter - considered "low normal" by the latest criteria - can be more than enough if the other three fertility factors are in place.

"The biggest risk of this test is that a guy who gets a very low sperm count might panic and end up getting more intervention than he really needed," said Goldfarb. "It might reassure some couples, but it might scare some couples, too."

Sperm counts can vary widely from week to week, Goldfarb said. So a man who rings in at 15 million per milliliter one week could hit 40 million the next. If the sperm count stays low, however, there are options.

"First we would look for anatomical problems," said Goldfarb, describing varicose veins in the scrotum or blockages to the penis that thwart sperm release. "Then we can look at hormonal things… If the problem can't be found or corrected, the simplest solution is to concentrate sperm and do intrauterine insemination. That way, there are more sperm getting closer to the fallopian tubes."

And if that doesn't work, in vitro fertilization allows a single sperm to fertilize an egg.

"We always try the simpler things first," said Goldfarb. "But if the couple is willing to be very aggressive, then we can still get a very good pregnancy success rate even if a man has a very low sperm count."