how to raise level without medication

In a healthy person platelet levels should remain within the normal range, so you need to have a thorough medical checkup to determine what is causing platelet deficiency. There is no sure way of raising platelets other than by correcting the underlying problem (are you on an anti-inflammatory, for instance?), and sometimes by pharmaceutical drugs that can boost platelet production. (See the thread Treatments for increasing platelet production)

However, there was this item from the website LifeExtension.

Anemia -Thrombocytopenia - Leukopenia : Online Reference For Health Concerns

I pass this on only as information -- as NoBlood does not recommend any particular treatments, especially unproven alternative or "natural" remedies. Here is the substance of the article:

A specific natural therapy to restore healthy platelet production is 5 capsules a day of standardized shark liver oil, containing 200 mg of alkylglycerols per capsule. Studies have shown that shark liver oil can boost the production of blood platelets. Studies have also shown the immune enhancement capabilities of shark liver oil (Pugliese et al. 1998). As will be discussed later, melatonin may be an effective and safe therapy to treat thrombocytopenia.
Shark oil capsules should be taken in high doses for a maximum period of only 30 days; otherwise, too many blood platelets might be produced.
Studies have shown that supplemental melatonin in doses of 10-40 mg a night can protect and restore normal blood cell production caused by the toxicity of chemotherapy (Lissoni et al. 1994, 1996, 1997a; Neri et al 1998). A study was performed in 80 patients with metastatic solid tumors to evaluate the benefits of melatonin. Patients received either chemotherapy alone or chemotherapy plus 20 mg each night of melatonin. Thrombocytopenia was significantly less frequent in patients receiving melatonin (Lissoni et al. 1997b).
Melatonin may also be an especially effective and safe therapy to correct thrombocytopenia, a condition characterized by a decrease in the number of blood platelets. A study was performed to evaluate the influence of melatonin on chemotherapy toxicity. Patients randomly received chemotherapy alone or chemotherapy plus melatonin (20 mg each evening). Thrombocytopenia was significantly less frequent in patients treated with melatonin (Lissoni 2002).