. Hi. My girl  (giant breed) was breed monday and again tuesday (day 13 and 14 in heat).Next day there were no interest from the dogs. 
The week before progesterontest was made 8/9 answer same day was 2,2 ng. New test  10/9 showed 3,7 ng.
According to vet. breed her 12/9-14/9 and so we did.
Now to my question , we took another bloodtest on tuesday 13/9 and it showed 16,4 ng!!!
To me it seems very high and I am afraid that we perhaps were to late. Anyone whith experience, was it to late?

I would be happy to breed on a reading of 16.4. In fact I would have done another breeding the day after. Ovulation occurs between 10-15 and two  days after that is the optimum time. So I reckon breeding the day after a reading of 16.4 would have been good and as I said I would have done the day after as well. Also don't forget healthy sperm can live inside a bitch for several days.

IMO this senario sound ok to me. A reading of 3.7ng would equate to 11.7nmol/l so I would have estimated a mating 3-5 days after getting that reading (personaly I re test until I get a reading of 15nmol/l or 4.7ng/l to be confident ovulation is impending) ) The reading on Tuesday at 16.4ng/l would equate to 52.15nmol/l which would be levels of progesterone indicating time for optimal fertility. If you hadn't mated already you could still mate Tues/Wed/Thurs.
So in short I would not think you were too late , if anything perhaps 24hrs too soon but with live mating with dogs with no fertility issues that soundn't really be a problem.

This is the potocol I use to interpret blood progesterones its in nmol/l
To convert to Progesterones in ng/l MULTIPLY BY  3.18 = progesterone in nmol/l
To convert nmmol/l DIVIDE BY 3.18 = progesterone in ng/l

0-2  nmol/L           Baseline concentrations too early to estimate ovulation 
3 - 6 nmol /L        Minimum 2 days before ovulation expected however result of 3 - 4 nmol/L may persist for a week or longer before increasing. Earliiest estimating breeding 4 - 6 days but could be longer (re test needed)
7 - 12 nmol/L   Minimum 1 day before ovulation. Estimated window for breeding 3 - 5 days but could be longer  ( re test recommended) 
13 - 18 nmol/L   Ovulation impending or just occurred. Estimated breeding window 2 - 4 days  
19 - 31 nmol/L   Ovulation recently occurred. Estimated breeding window 1 - 3 days
32 - 64 nmol/L   Ova have matured, optimal potential for fertility.  Estimated breeding window  0 - 2 days
65 - 90 nmol/L   Ova have matured but aging, decreased potential for fertility.  Breed  at once
Above 90 nmol/L    Too late 

K

Thank you both for your replies. Oops, the breeding was  13/9 and 14/9( I wrote wrong) så it looks like it was actually in right time!!  LOL.  I really want puppies so I hope she is pregnant.
Thanks again for the answers!!!

16.4 ng/ml is spot on for a mating.

I was going to say - ng readings will be lower then than nmol - and optimum breeding reading would be around 20 ng ?