Notice that he dropped his hemoglobin by about 12%. Not bad for about an hour of time, eh?
2. Lower Your TRT Dose. If you have high hemoglobin or hematocrit from testosterone therapy, then your doctor may require you to lower your dose. This is not always a bad thing as some men are actually taking more than they actually need, which can lead to side effects in both the long and short term. See my page on The Side Effects of Testosterone Therapy for more information.
3. Drink Water. It is important to remember that hemoglobin is very dependent on your hydration levels. If you were dehydrated when you had your blood draw, this could have made things worse. If you think you were dehydrated, discuss a retest with your doctor.
4. Hyperthyroidism. Hypothyroidism can lower your RBC counts and hyperthyroidism can raise them some.  If you haven’t checked your thyroid function lately, this might be wise. And don’t forget to get a full workup, including antibodies, if you can afford it. See my page on Testosterone and the Thyroid for more details.
5. Transdermal (Topical) Testosterone? One research summary stated that topical lead, in general, to lowered levels versus intramuscular injections:
“Intramuscular testosterone is the only form that significantly increases hematocrit above normal levels. However, it does so strongly, with up to a 6% change from baseline. The runner-up is testosterone gel, with an average increase of 2.5% over baseline levels.” 
Therefore, if you are on intramuscular injections and struggling with high hematocrit or hemoglobin, going on topicals may help a little. Discuss with your physician. NOTE: A cheap alternative is Compounded Testosterone Creams and Gels.
6. Avoid Red Meats. It is interesting because one of the criticisms that meat eaters level against vegetarians is that plant foods have many “anti-nutrients” that can slow down or bind with minerals such as iron. For example, organizations like Weston Price love to castigate vegetarians for their phytic acid consumption. Phytic acid is present in plant foods and binds to iron, magnesium, phosphorous and calcium. It can, if overconsumed, lead to mineral deficiences. However, Dr. Bernard points out that usually it is likely very health protective for most people, because these minerals, as in the case of zinc and iron, have been found to be neurotoxic at even relatively low levels of tissue accumulation. Research has also shown that too much iron also contributes to heart disease and there may be a link to colon cancer as well. 
So avoiding red meats, which are high in heme iron, stands a good chance of lowering your hemoglobin scores and protecting your long term health unless some other preventative action is taken (such as giving blood). For other cautions about meat consumption, especially red meat, seemy link on The Risks of Meat Consumption.
As a verification, one study of vegetarians and non-vegetarians found that females had significantly lower hemoglobin levels. Males had lower levels but it may not have been statistically significant.  However, another study was more definitive and concluded: “It was found that hemoglobin, hematocrit, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, white blood cells, neutrophils, serum ferritin and serum vitamin B12 in vegetarian were significantly lower than control subjects.”  The ferritin is a key measure, by the way, because it indicates that tissue levels of iron are lower and thus will likely cause less permanent damage. (This study did show that some vegetarians were iron deficient it should be noted.)
7. Fix Sleep Apnea. One of our senior posters was told that sleep apnea tends to thicken the blood in this Peak Testosterone Forum thread. And, sure enough, the studies confirm this as well.  So, if your hematocrit, hemoglobin or RBC’s are running high, think about getting tested for sleep apnea. A recent study commented that “one possible explanation is that repeated episodes of nocturnal hypoxia lead to a hypercoagulable state that predisposes patients to thrombotic events. There is evidence supporting a wide array of hematological changes that affect hemostasis (eg, increased hematocrit, blood viscosity, platelet activation, clotting factors and decreased fibrinolytic activity).”
8. Inflammation. Hepcidin activity can be governed by inflammation. Checking for infections, CRP levels, etc. and then treating the underlying cause may help.