Low molecular weight heparin

Low molecular weight heparin is administered subcutaneously, usually in the abdomen, once a day

Low molecular weight heparin (Clexane®, Hibor®, Fragmin®, Innohep®) is  administered subcutaneously, usually in the abdomen, once a day.

It can be injected in the forearm or in the inner part of the thigh if the abdomen is not an option (in recent surgery patients or in advanced pregnancy). The effect is the same, but it may hurt a little more.

The prick is not too bad, because the needle and syringe are already pre-loaded and are small. The following instructions facilitate its application:

  1. positioned in a supine position (lying face up)
  2. take a fold of skin from the abdomen with one hand. If it is tight, the pain of the prick will be less
  3. with the other hand, prick yourself with the needle in a vertical position, not slanted, and without having previously removed the existing air bubble. So the air is inside the needle and we make sure that we have introduced all of the drug
  4. it is recommended to change the injecting area every day, since the prick is likely to cause small bruises

Unlike with antivitamin K drugs, you do not have to adjust: the doses of the medicine, it is a fixed dose that is administered once or twice a day, depending on the disease and the patient’s weight.

There is no specific time of the day that it is better than another, but it is important that the drug is administered at the same time every day. If you forget it one day, the best is to check with your doctor.


Two months ago I was diagnosed with a superficial thrombophlebitis in my left leg and they told me I needed Clexane 40 mg injections for 90 days. Today I woke up with pain in my right calf and I’m not sure if it is soreness of it might be a DVT. I can see that I have both legs equal, I don’t have any varices. Could I have a DVT or is it just that I’m sore?

If you have had a superficial thrombophlebitis a few days ago and now your calf from the other leg hurts more, you may be having a new thrombosis in the other leg. I suggest you to visit your doctor, he will perform an echo-doppler in order to know if you are having a deep venous thrombosis (DVT), a superficial thrombosis or maybe it has nothing to do with the cause of your pain.

I am pregnant and I would like to know if low molecular weight heparin injections have any problem over the fetus.

You don’t need to worry. Low molecular weight heparin in prophylaxis dose does not have any risk on the fetus. They are efficient and secure.

I would like to know if there is any problem for having suspended Clexane injections for 48h.

We can’t be 100% sure. If you have not experienced any symptom, most likely nothing has happened. Just make sure this doesn’t happen again.


Do you have questions?

If there are any aspects of thrombosis and/or pulmonary embolism that you are not sure about, you can contact us, and our specialists will answer you shortly. This cannot replace the visit to your doctor