Based upon your background I would conclude you don't have an opiate tolerance, so your body should respond to a low dose of morphine very well. I wouldn't recommend anything other than taking the pills orally. Do not attempt to crush them, snort them, or IV them. All of which can be done with pure morphine.
Since you have no tolerance to opiates, or a very low tolerance, I'd say start with no more than 10mg. I have a big tolerance to opiates, and even I still feel 10mg of morphine. To play it the safest way possible, I'd say take 1 5mg pill, wait 30-40 minutes and see how you feel. If there's no nausea or adverse effects, then you can up the dose.
Based upon your low opiate tolerance, and also depending on your weight. I wouldn't recommend taking over 15mg at one time until you know you're comfortable with the drug.
I used morphine recreationally once (thankfully no addiction from it), and I used to snort 5mg tabs at a time, and I would do up to 40mg per day sometimes. And I weigh about 220lbs, but just remember everyone is different. What works for me or someone else, could be potentially life threatening to you. When I did 5mg at a time, even with my tolerance, I usually felt a nice high for about 30-40 minutes.
I don't like to preach, but I would like to remind you that morphine is highly addictive and very strong. In a MG per MG comparison, morphine is stronger than Oxycodone. Watch your dosages, and if you begin to notices signs of an addiction, which usually starts as a strong craving then stop taking them immediately before you cross the border into physical addiction like some of us suffer from.
