pberm

i am a 49 year old male ,average weight ,good blood pressure, active. i have been donating blood for about 25 years and until recently have never been turned away because of low hemoglobin values. the last 3 out of 4 attempts i have been turned away, i try about every 2 months to give. today my level was at its lowest ,at 10 g/dl. i eat a normal diet including red meat ,all fruits, raisens, beans, breads, cereals, dairy products. i do drink about 12 ounces of coffee per day but drink at least one to two quarts of water after. i take an A to Z multivitamin daily which includes 18 mg of iron. i do not have a complete blood test available now to show you. i do feel a certain amount of fatigue. at what point should i make my doctor aware of my lowering hemoglobin level ? thanks paul