I have not been able to find a reliable test for Serotonin levels. For Heparin treatment you need to consult a properly trained and registered medical Doctor. As i live in the UK i dont know how the medical system in the USA works so cant advise you on where to go or how to go about getting the right advice.
In the US, its easy to get a LabCorp test for neurotransmitters. A Genova Diagnostics NutrEval can tell you if you have all the cofactors for neurotransmitter production.
And a functional medicine doctor, which could be an MD, ND, DC, DO, or ARNP should be able to help.
One day, I found myself lying on the couch, unable to motivate myself to move. My naturopathic doctor suggested taking 6g of tyrosine, which instantly perked me up, after I tested low for dopamine and tyrosine.
Somewhere, some of these researchers found that we tend to be low in dopamine.
500mg of tyrosine is not enough to do much for me. I still need 3g daily and mood and motivation are fine.
Amino acids are important. We seem to go through them, so supplementing them is not a bad idea. Robert Erdman's book, The Amino Revolution, while older, is a good beginning primer on using aminos. I got a copy for $1 on Amazon. Julia Ross has some good ideas, too.