Jason Day has no idea why he is suffering from dizzy spells and lethargy at times but the world No.8 hopes for answers soon ahead of the rest of the majors.

Day will attempt to power through it at his 'home' tournament this week as he awaits results of several blood tests and sleep studies designed to come up with answers for his troubling mystery ailments, issues which have ramped up over the last month.

As a member of Muirfield Village and a nearby resident Day is a local favourite at Jack Nicklaus' Memorial Tournament but expectations have been tempered as he battles to complete a round of golf with full energy.

First afflicted during the final round of the Zurich Classic in New Orleans in late April where he faded from the lead into a tie for fourth the 27-year-old followed it up with a 0-3 performance in his World Golf Championship Match Play Championship title defence and a missed cut, with a second round 81, in the Players Championship.

The Queenslander withdrew from last week's Byron Nelson Championship after not being able to complete the Pro-am thanks to further dizziness.

With the US Open at Chambers Bay just two weeks away the timing is not ideal.

"I'm still not 100 per cent so my expectations aren't super high but in saying that sometimes in golf that is the best place to be," Day said after getting through nine holes of practice on Tuesday without too much trouble.

"I've had this at times through my whole career but it has really come up since the 13th hole on the final day at New Orleans.

"I just lost all my energy and have had moments where I feel it from my feet all the way up my body, just the shakes and loss of strength through my hands and of course dizziness.

"At the end of the day we are doing everything we can to find an answer and from that hopefully we can move forward and get on top of it."

Doctors will run further tests in the coming weeks as they try to come up with possibilities which could range from a lingering viral infection like glandular fever or chronic fatigue syndrome to a simple case of overtraining given Day's penchant for hitting the weights, sometimes twice a day.

His adrenaline will surely be pumping come Thursday's opening round, having been paired with new friend and 14-time major winner Tiger Woods plus USA 'bad boy' Patrick Reed.

But whether he can improve on a career best T27 finish here despite his local knowledge remains to be seen.

"It should be a great week and it is certainly a good pairing to start," Day said.

"I have a lot of support here obviously and in the past I have overplayed this course, maybe trying too hard in front of everyone.

"It's a second shot course, don't over think it, just don't short side yourself and make some putts and you'll be in the mix."

Last start winner Steven Bowditch plus Greg Chalmers, Matt Jones, Marc Leishman, John Senden and Cameron Smith join Day in the field.