The requirement to have travel insurance was introduced at European level for holders of a short-stay (type C) or long-stay visa valid as a Schengen visa (type D+C).
Therefore, any individual wishing to enter the Schengen area (including Belgium) with this type of visa must also be able to prove that they have taken out valid travel insurance, either individual or group insurance, covering the cost of repatriation on medical grounds, urgent medical treatment and/or urgent hospital treatment. The insurance must be valid throughout all of the Schengen countries and must cover the whole duration of the stay. The minimum cover is EUR 30,000.
As a rule, you must take out insurance in your country of residence. If your host takes out the insurance for you, he/she must do so in his/her own country of residence.
To find out which insurance policies are accepted, you should enquire at the relevant Belgian embassy or consulate (or the embassy representing Belgium).