Mary, apart from Cranberry juice, there are no foods that you shouldn't eat whilst on warfarin.
Healthcare providers will tell you to eat a healthy diet whether your on warfarin or not! Eating an unhealthy diet will not affect your INR so there is no reason why a takeaway should affect your INR, unless of course you drink more than your usual amount of alcohol with it!
The only foods that are particularly rich in Vit K are green leafy ones. Other foods might contain Vit K, but not in high enough amounts to affect INR, so you don;t need to worry about how much of those you eat..If you eat a relatively constant amount of Vit K rich veg then your INR won't be affected.
If, however, you don't usually eat any Vit K rich foods and one day in the week you eat a Vit K rich meal, for example spinach salad , then your INR will be affected.
The key in warfarin therapy is consistent intake, or dose, of Vit K rich foods, alcohol and other medications (including over the counter meds and, importantly,health supplements and herbal remedies.
Quite often people forget about herbal remedies. St Johns Wort , for example can have a drastically increase INR , and can be dangerous if taken with many other medicines and certain foods.
Over the counter medicines that may be taken on an occasional rather than consistent basis include Indigestion and heartburn remedies. They may reduce warfarin absorbtion and thus reduce the INR.
I worked in a hospital anticoagulation service for 4 years as a Clinical Nurse Specialist. We managed almost 2000 outpatients and up to 40 inpatients who were on warfarin and the most common reasons for unstable INR's were, in order of importance
Missed or incorrect dose(s) of warfarin taken
Changes in other medications (ie altered dosage or a new medication)
Alcohol intake (usually binge drinking)
Increase in severity of other medical conditions eg Kidney, liver, heart or breathing disorders
Changes in "meal replacement" drinks (ie starting/stopping or changes in the amount)
If your INR has never been stable then it may be one of the above that's affecting it.
Of course, there is a certain skill in "dosing " warfarin, and here in the UK specialist anticoagulation services came about because GPs were only managing a few patients and often didn't have the knowledge or skills to do a good job. At the same time there was an awareness that many people who were on warfarin for stroke prevention (often elderly people with Atrial Fibrillation) were having TIAs or strokes because their anticoagulation wasn't being managed effectively.
Regarding heparin injections, these are given in the same dose every day. The dose is based on patient weight and doesn't require monitoring. The INR was used to adjust the warfarin dose because at the same time you were having the heparin injections you were also on warfarin. Once the INR reached your therapeutic range (2-3?) then the heparin injections are no longer required. The heparin injections are used at the beginning of anticoagulation therapy because the first injection works almost immediately to anticoagulate the blood, whereas warfarin takes a while to have an effect and the dose required to get the blood to the required level of anticoagulation varies in individuals.